// In the Name of Allah
#include<bits/stdc++.h>
using namespace std;
#pragma GCC optimize("Ofast,unroll-loops,fast-math")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4.1,avx,avx2,sse4.2,popcnt,tune=native")
typedef long long ll;
#define F first
#define S second
#define pii pair<int, int>
#define pb push_back
#define pp pop_back
#define all(x) x.begin(), x.end()
#define MX(x, y) ((b[x] > b[y])? x : y)
const int LG = 21, N = 3e5 + 7, M = 1e4 + 7, K = 5e5 + 7, mod1 = 1000992299, base1 = 760, mod2 = 1e9 + 9, base2 = 600;
string s, a[M];
int n, q, p[N][LG], m, mx[2 * N], b[N];
ll h1[N], h2[N], rtb1[N], rtb2[N];
unordered_set<int64_t> st[K];
void ip() {
cin >> n >> q;
for (int i = 0; i < n; i++)
cin >> a[i];
cin >> s;
m = s.size();
}
int bp1(int x, int y) {
if (y < 2) return y? x : 1;
ll tmp = bp1(x, y / 2);
tmp = tmp * tmp % mod1;
return (y & 1)? tmp * x % mod1 : tmp;
}
int bp2(int x, int y) {
if (y < 2) return y? x : 1;
ll tmp = bp2(x, y / 2);
tmp = tmp * tmp % mod2;
return (y & 1)? tmp * x % mod2 : tmp;
}
void solve() {
for (int i = 0; i < n; i++) {
ll v1 = 0, tb1 = 1, v2 = 0, tb2 = 1;
for (int j = 0; j < a[i].size(); j++) {
v1 = (v1 + tb1 * a[i][j]) % mod1;
tb1 = tb1 * base1 % mod1;
v2 = (v2 + tb2 * a[i][j]) % mod2;
tb2 = tb2 * base2 % mod2;
st[j + 1].insert((v1 << 31) | v2);
}
}
ll rb1 = bp1(base1, mod1 - 2);
rtb1[0] = 1;
for (int i = 1; i <= m; i++)
rtb1[i] = rtb1[i - 1] * rb1 % mod1;
ll tb1 = 1;
for (int i = 1; i <= m; i++)
h1[i] = (h1[i - 1] + s[i - 1] * tb1) % mod1, tb1 = tb1 * base1 % mod1;
ll rb2 = bp2(base2, mod2 - 2);
rtb2[0] = 1;
for (int i = 1; i <= m; i++)
rtb2[i] = rtb2[i - 1] * rb2 % mod2;
ll tb2 = 1;
for (int i = 1; i <= m; i++)
h2[i] = (h2[i - 1] + s[i - 1] * tb2) % mod2, tb2 = tb2 * base2 % mod2;
for (int i = 0; i < m; ++i) {
int l = i, r = m + 1;
while (r - l > 1) {
int mid = (l + r) >> 1;
ll v1 = (h1[mid] - h1[i] + mod1) * rtb1[i] % mod1;
ll v2 = (h2[mid] - h2[i] + mod2) * rtb2[i] % mod2;
if (st[mid - i].count((v1 << 31) | v2))
l = mid;
else
r = mid;
}
b[i] = l;
mx[m + i] = i;
}
for (int i = m - 1; i; --i)
mx[i] = MX(mx[i << 1], mx[i << 1 | 1]);
for (int i = m - 1; ~i; --i) {
int res = i;
for (int l = i + m, r = min(b[i] + 1, m) + m; l < r; l >>= 1, r >>= 1) {
if (l & 1) res = MX(res, mx[l]), l++;
if (r & 1) r--, res = MX(res, mx[r]);
}
p[i][0] = res;
for (int j = 1; j < LG; ++j)
p[i][j] = p[p[i][j - 1]][j - 1];
}
while (q--) {
int l, r;
cin >> l >> r;
if (b[l] >= r) {
cout << 1 << '\n';
continue;
}
int res = 0;
for (int i = LG - 1; ~i; --i)
if (b[p[l][i]] < r)
res |= (1 << i), l = p[l][i];
cout << ((res > m)? -1 : res + 2) << '\n';
}
}
int32_t main() {
ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
ip(), solve();
return 0;
}
