import java.io.*;
import java.util.*;public class Main    {public static void main(String[] args) {Scanner cin = new Scanner (System.in);int r = cin.nextInt ();int c = cin.nextInt ();int n = cin.nextInt ();int k = cin.nextInt ();int[][] a = new int[12][12];for (int i=0; i<n; ++i)  {int x = cin.nextInt ();int y = cin.nextInt ();a[x][y] = 1;}int ans = 0;for (int sx=1; sx<=r; ++sx)  {for (int lx=0; sx+lx<=r; ++lx) {for (int sy=1; sy<=c; ++sy) {for (int ly=0; sy+ly<=c; ++ly) {int cnt = 0;for (int i=sx; i<=sx+lx; ++i) {for (int j=sy; j<=sy+ly; ++j)  {if (a[i][j] == 1)    cnt++;if (cnt >= k)   break;}}if (cnt >= k)   ans++;}}}}System.out.println (ans);}
}

#include <bits/stdc++.h>const int N = 2e5 + 5;
int a[N], b[N];
int n;int main()    {scanf ("%d", &n);int tot1 = 0, tot2 = 0;for (int x, i=0; i<n; ++i)   {scanf ("%d", &x);if (x != 0)    a[tot1++] = x;}for (int x, i=0; i<n; ++i)  {scanf ("%d", &x);if (x != 0)    b[tot2++] = x;}int s = 0;for (; s<tot2; ++s)   {if (b[s] == a[0])    break;}bool flag = true;for (int i=0; i<tot1; ++i)   {if (b[(i+s)%(n-1)] != a[i])  {flag = false; break;}}if (flag)   puts ("YES");else puts ("NO");return 0;
}

#include <bits/stdc++.h>typedef long long ll;
int s[41], x[41];
ll dp[41][4][2];void updata(int id) {if (s[id] == x[id])  {if (s[id] == 0)  {   //0 0if (id == 0) {dp[id][2][0] = dp[id][3][1] = 1;}else    {for (int j=0; j<4; ++j)  {dp[id][2][0] += dp[id-1][j][0];dp[id][3][1] += dp[id-1][j][0];}}}else  {           //1 1if (id == 0) {dp[id][0][0] = dp[id][1][0] = 1;}else    {for (int j=0; j<4; ++j)  {dp[id][0][0] += dp[id-1][j][0];dp[id][1][0] += dp[id-1][j][0];}}}}else {if (s[id] == 0)  {   //0 1for (int j=0; j<4; ++j)  {dp[id][0][1] += dp[id-1][j][1];dp[id][1][1] += dp[id-1][j][1];}}else   {           //1 0for (int j=0; j<4; ++j)  {dp[id][2][0] += dp[id-1][j][1];dp[id][3][1] += dp[id-1][j][1];}}}
}int main() {ll S, X;   std::cin >> S >> X;if (X == 0)    {puts ("1");  return 0;}bool same = false;if (S == X)  same = true;int n = 0, m = 0;while (S)   {if (S & 1) s[n++] = 1;else  s[n++] = 0;S >>= 1;}while (X) {if (X & 1) x[m++] = 1;else  x[m++] = 0;X >>= 1;}int len = std::max (n, m);for (int i=0; i<len; ++i)    {updata (i);}ll ans = 0;for (int i=0; i<4; ++i)  {ans += dp[len-1][i][0];}if (same && ans >= 2)    ans -= 2;std::cout << ans << '\n';return 0;
}

import java.io.*;
import java.util.*;public class Main    {static int[][] C;static int[] A;static int n;static void updata(int i, int j, int x)   {while (i <= n) {C[i][j] += x;i += i & -i;}}static int query(int i, int j)  {int ret = 0;while (i > 0)  {ret += C[i][j];i -= i & -i;}return ret;}static int min(int a, int b)    {if (a < b)  return a;else   return b;}public static void main(String[] args)    {Scanner cin = new Scanner (new BufferedInputStream (System.in));n = cin.nextInt ();int k = cin.nextInt ();int a = cin.nextInt ();int b = cin.nextInt ();int q = cin.nextInt ();C = new int[n+5][2];A = new int[n+5];for (int i=0; i<q; ++i)    {int op = cin.nextInt ();if (op == 1)    {int d = cin.nextInt ();int e = cin.nextInt ();int tmp = A[d];   A[d] += e;updata (d, 0, min (b, A[d]) - min (b, tmp));updata (d, 1, min (a, A[d]) - min (a, tmp));}else   {int p = cin.nextInt ();int ans = query (p - 1, 0) + query (n, 1) - query (p+k-1, 1);System.out.println (ans);}}}
}

#include <bits/stdc++.h>typedef long long ll;
const int N = 2e5 + 5;
int dque[N];
std::pair<int, int> station[N];
int d, n, m;int main()  {scanf ("%d%d%d", &d, &n, &m);for (int i=0; i<m; ++i)   {scanf ("%d%d", &station[i].first, &station[i].second);}station[m++] = std::make_pair (0, 0);station[m++] = std::make_pair (d, 0);std::sort (station, station+m);for (int i=0; i<m-1; ++i)   {if (station[i].first + n < station[i+1].first)    {puts ("-1"); return 0;}}int qs = 0, qe = 0, now = 0;  ll ans = 0;for (int i=0; i<m; ++i)   {int x = station[i].first, p = station[i].second;while (qs < qe && station[dque[qs]].first + n < x)    {ans += 1ll * (station[dque[qs]].first + n - now) * station[dque[qs]].second;now = station[dque[qs]].first + n;qs++;}ans += 1ll * (x - now) * station[dque[qs]].second;now = x;while (qs < qe && station[dque[qe-1]].second > p)    {qe--;}dque[qe++] = i;}std::cout << ans << '\n';return 0;
}

#include <bits/stdc++.h>const int N = 2e5 + 5;
struct DP {int sum, mx;DP operator + (const DP &rhs) const {return DP {sum + rhs.sum, std::max (mx, rhs.mx)};}
};
int a[N], total[N], down[N], dp[N];
bool good[N];
std::vector<int> edge[N];
int n, k;void DFS(int u, int fa)    {total[u] = 1;int sum = 0, mx = 0;for (auto v: edge[u])  {if (v == fa) continue;DFS (v, u);total[u] += total[v];if (down[v] == total[v]) {sum += total[v];} else {mx = std::max (mx, down[v]);}}down[u] = sum + mx + 1;if (!good[u]) down[u] = 0;
}void DFS2(int u, int fa, int up)   {　　　　//learn from touriststd::vector<int> children;int sum = 0, mx = 0;for (auto v: edge[u])    {if (v == fa) continue;if (down[v] == total[v]) {sum += down[v];} else {mx = std::max (mx, down[v]);}children.push_back (v);}if (up == n - total[u]) {sum += up;} else {mx = std::max (mx, up);}dp[u] = sum + mx + 1;if (!good[u])   dp[u] = 0;int sz = children.size ();if (sz == 0)    return ;std::vector<DP> predown (sz + 1);predown[0] = {0, 0};for (int i=0; i<sz; ++i) {int v = children[i];predown[i+1] = predown[i];if (down[v] == total[v]) {predown[i+1].sum += down[v];} else {predown[i+1].mx = std::max (predown[i+1].mx, down[v]);}}std::vector<DP> sufdown (sz + 1);sufdown[sz] = {0, 0};for (int i=sz-1; i>=0; --i)  {int v = children[i];sufdown[i] = sufdown[i+1];if (down[v] == total[v]) {sufdown[i].sum += down[v];} else {sufdown[i].mx = std::max (sufdown[i].mx, down[v]);}}for (int i=0; i<sz; ++i) {int v = children[i];DP now = predown[i] + sufdown[i+1];if (up == n - total[u]) {now.sum += up;} else {now.mx = std::max (now.mx, up);}int new_up = now.sum + now.mx + 1;if (!good[u]) new_up = 0;DFS2 (v, u, new_up);}
}bool check(int v)  {for (int i=1; i<=n; ++i)    good[i] = (a[i] >= v);DFS (1, 0);DFS2 (1, 0, 0);for (int i=1; i<=n; ++i)    {if (dp[i] >= k)    return true;}return false;
}int main() {scanf ("%d%d", &n, &k);for (int i=1; i<=n; ++i)   {scanf ("%d", a+i);}for (int u, v, i=1; i<n; ++i)  {scanf ("%d%d", &u, &v);edge[u].push_back (v);edge[v].push_back (u);}int low = 0, high = 1000005;while (low < high)  {int mid = (low + high + 1) >> 1;if (check (mid))  {low = mid;} else {high = mid - 1;}}printf ("%d\n", low);return 0;
}