#include<cstdio>
#include<algorithm>
#include<iostream>
#include<cstring>
#include<cmath>
#include<cctype>
#include<set>
#include<queue>
#include<vector>
#include<map>
#include<bitset>
using namespace std;
typedef long long LL;inline int read() {int x=0,f=1;char ch=getchar();for(;!isdigit(ch);ch=getchar())if(ch=='-')f=-1;for(;isdigit(ch);ch=getchar())x=x*10+ch-'0';return x*f;
}const int N = 600005;
char s[N];
int t1[N], t2[N], c[N], sa[N], rnk[N], ht[N], f[N][21], Log[N];
void getsa(int n) {int m = 130, i, *x = t1, *y = t2;for (i = 1; i <= m; ++i) c[i] = 0;for (i = 1; i <= n; ++i) x[i] = s[i], c[x[i]] ++;for (i = 1; i <= m; ++i) c[i] += c[i - 1];for (i = n; i >= 1; --i) sa[c[x[i]]--] = i;for (int k = 1; k <= n; k <<= 1) {int p = 0;for (i = n - k + 1; i <= n; ++i) y[++p] = i;for (i = 1; i <= n; ++i) if (sa[i] > k) y[++p] = sa[i] - k;for (i = 1; i <= m; ++i) c[i] = 0;for (i = 1; i <= n; ++i) c[x[y[i]]] ++;for (i = 1; i <= m; ++i) c[i] += c[i - 1];for (i = n; i >= 1; --i) sa[c[x[y[i]]]--] = y[i];swap(x, y);p = 2;x[sa[1]] = 1;for (i = 2; i <= n; ++i) x[sa[i]] = (y[sa[i]] == y[sa[i - 1]] && y[sa[i] + k] == y[sa[i - 1] + k]) ? p - 1 : p ++;if (p > n) break;m = p;}for (i = 1; i <= n; ++i) rnk[sa[i]] = i;ht[1] = 0;int k = 0;for (i = 1; i <= n; ++i) {if (rnk[i] == 1) continue;if (k) k --;int j = sa[rnk[i] - 1];while (i + k <= n && j + k <= n && s[i + k] == s[j + k]) k ++;ht[rnk[i]] = k;}for (i = 1; i <= n; ++i) f[i][0] = ht[i];for (i = 2; i <= n; ++i) Log[i] = Log[i >> 1] + 1;for (int j = 1; j <= Log[n]; ++j) for (i = 1; i + (1 << j) - 1 <= n; ++i) f[i][j] = min(f[i][j - 1], f[i + (1 << (j - 1))][j - 1]);
}
int LCP(int i,int j) {i = rnk[i], j = rnk[j];if (i > j) swap(i, j);i ++;int k = Log[j - i + 1];return min(f[i][k], f[j - (1 << k) + 1][k]);
}
int LCP2(int i,int j) {i ++;int k = Log[j - i + 1];return min(f[i][k], f[j - (1 << k) + 1][k]);
}set<int> sk;
int n, k, rev[N];bool check(int len) {int l = *sk.begin();set<int>::iterator it = sk.end(); it --;int r = *it;return LCP2(l, r) >= len;
}
int check2(int i,int j,int len) {if (sk.size() >= 2 && !check(len)) return 0;int a = min(len - 1, LCP(rev[i - 1], rev[i - 1 + len]));if (j + len > n) return 0;int b = min(len - 1, LCP(j, j + len));return max(0, b - (len - a) + 1);
}
int main() {freopen("sutoringu.in", "r", stdin);freopen("sutoringu.out", "w", stdout);n = read(), k = read();scanf("%s", s + 1);s[n + 1] = '#';for (int i = 1; i <= n; ++i) s[i + n + 1] = s[n - i + 1], rev[n - i + 1] = i + n + 1;getsa(n + n + 1);LL ans = 0;for (int len = 1; len <= n; ++len) {sk.clear();for (int i = 1; i <= n; i += len) {sk.insert(rnk[i]);if (sk.size() > k) sk.erase(rnk[i - len * k]);if (sk.size() == k) ans += check(len);}if (len == 1) continue;sk.clear();for (int i = len + 1; i <= n; i += len) {sk.insert(rnk[i]);if (sk.size() > k - 1) sk.erase(rnk[i - len * (k - 1)]);if (sk.size() == k - 1) ans += check2(i - (k - 2) * len, i, len);}}cout << ans;return 0;
}