#include<bits/stdc++.h>
#define LL long long
#define LD long double
#define ull unsigned long long
#define fi first
#define se second
#define mk make_pair
#define PLL pair<LL, LL>
#define PLI pair<LL, int>
#define PII pair<int, int>
#define SZ(x) ((int)x.size())
#define ALL(x) (x).begin(), (x).end()
#define fio ios::sync_with_stdio(false); cin.tie(0);using namespace std;const int N = 5e5 + 7;
const int inf = 0x3f3f3f3f;
const LL INF = 0x3f3f3f3f3f3f3f3f;
const int mod = 998244353;
const double eps = 1e-8;
const double PI = acos(-1);template<class T, class S> inline void add(T& a, S b) {a += b; if(a >= mod) a -= mod;}
template<class T, class S> inline void sub(T& a, S b) {a -= b; if(a < 0) a += mod;}
template<class T, class S> inline bool chkmax(T& a, S b) {return a < b ? a = b, true : false;}
template<class T, class S> inline bool chkmin(T& a, S b) {return a > b ? a = b, true : false;}int n, m, c[N];
int prefix[N];
int nex[N][20];struct Line {int l, r;bool operator < (const Line &rhs) const {if(l == rhs.l) return r > rhs.r;return l < rhs.l;}
} a[N];int main() {scanf("%d%d", &n, &m);for(int i = 1; i <= n; i++) scanf("%d%d", &a[i].l, &a[i].r), a[i].r--;sort(a + 1, a + 1 + n);int nn = n; n = 1;for(int i = 2; i <= nn; i++)if(a[i].r > a[n].r) a[++n] = a[i];for(int i = 1; i <= n; i++) {c[a[i].l]++;c[a[i].r + 1]--;}if(!c[0]) prefix[0] = 1;for(int i = 1; i <= 500000; i++) {c[i] += c[i - 1];if(!c[i]) prefix[i] = 1;prefix[i] += prefix[i - 1];}for(int i = 1, j = 2; i <= n; i++) {j = max(i + 1, j);while(j <= n && a[j].l <= a[i].r + 1) j++;nex[i][0] = j - 1 == i ? 0 : j - 1;}for(int j = 1; j < 20; j++)for(int i = 1; i <= n; i++)nex[i][j] = nex[nex[i][j - 1]][j - 1];while(m--) {int x, y; scanf("%d%d", &x, &y);y--;int cnt = prefix[y];if(x) cnt -= prefix[x - 1];if(cnt) {puts("-1");} else {int p = lower_bound(a + 1, a + 1 + n, Line{x + 1, inf}) - a - 1;if(a[p].r >= y) {puts("1");} else {int ans = 0;for(int i = 19; i >= 0; i--) {if(nex[p][i] && a[nex[p][i]].r < y) {p = nex[p][i], ans += (1 << i);}}printf("%d\n", ans + 2);}}}return 0;
}