// 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()
const int N = 503, M = 1e4 + 7, K = 5e5 + 7;
string s, a[M];
int n, q, dp[N][N], c, t[K][26], m;
void add(int id) {
int p = 0;
for (int i = 0; i < a[id].size(); i++) {
if (!t[p][a[id][i] - 'a'])
t[p][a[id][i] - 'a'] = ++c;
p = t[p][a[id][i] - 'a'];
}
}
void ip() {
cin >> n >> q;
for (int i = 0; i < n; i++) {
cin >> a[i];
add(i);
}
cin >> s;
m = s.size();
}
void solve() {
for (int d = 1; d <= m; d++)
for (int l = 0; l + d <= m; l++) {
int r = l + d;
dp[l][r] = m + 1;
for (int i = l, p = 0; i < r && (p = t[p][s[i] - 'a']); i++)
dp[l][r] = min(dp[l][r], 1 + dp[i + 1][r]);
}
while (q--) {
int l, r;
cin >> l >> r;
cout << ((dp[l][r] == m + 1)? -1 : dp[l][r]) << '\n';
}
}
int32_t main() {
ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
ip(), solve();
return 0;
}
