#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
cerr << " " << H;
debug_out(T...);
}
#define debug(...) cerr << "(" << #__VA_ARGS__ << "):", debug_out(__VA_ARGS__)
#define all(x) x.begin(), x.end()
#define MP(x, y) make_pair(x, y)
#define F first
#define S second
const int maxn = 1e6 + 10;
const int lg = 20;
int n, q, a[maxn], sz, suf[maxn], tmp[maxn], cnt[maxn], rnk[maxn << 1], l[maxn], r[maxn], lcp[lg][maxn], rmq[lg][maxn], dp[lg][maxn];
int L[maxn], R[maxn], ptr[maxn], ans[maxn];
string s, t;
vector<int> st;
int w = 1;
bool sufcmp(int x, int y){
return (rnk[x] == rnk[y]? rnk[x+w] < rnk[y+w]: rnk[x] < rnk[y]);
}
void sufarr(string &s){
int n = s.size();
for (int i = 0; i < n; i++){
if (s[i] == '#') continue;
rnk[i] = s[i] - 'a' + 1;
}
for (; ; w <<= 1){
memset(cnt, 0, sizeof cnt);
for (int i = 0; i < n; i++){
cnt[rnk[i+w]]++;
}
for (int i = 1; i <= max(26, n); i++){
cnt[i] += cnt[i-1];
}
for (int i = 0; i < n; i++){
tmp[--cnt[rnk[i+w]]] = i;
}
memset(cnt, 0, sizeof cnt);
for (int i = 0; i < n; i++){
cnt[rnk[i]]++;
}
for (int i = 1; i <= max(26, n); i++){
cnt[i] += cnt[i-1];
}
for (int i = n-1; ~i; i--){
suf[--cnt[rnk[tmp[i]]]] = tmp[i];
}
tmp[suf[0]] = 1;
for (int i = 1; i < n; i++){
tmp[suf[i]] = tmp[suf[i-1]] + sufcmp(suf[i-1], suf[i]);
}
for (int i = 0; i < n; i++) rnk[i] = tmp[i];
if (rnk[suf[n-1]] == n) break;
}
}
void buildlcp(string &s){
int n = s.size();
int k = 0;
for (int i = 0; i < n; i++){
if (rnk[i] == n) continue;
while(i + k < n && suf[rnk[i]] + k < n && s[i+k] == s[suf[rnk[i]]+k]) k++;
lcp[0][rnk[i]] = k;
if (k) k--;
}
for (int i = 1; i < lg; i++){
for (int j = 1; j + (1 << i) - 1 <= n; j++){
lcp[i][j] = min(lcp[i-1][j], lcp[i-1][j + (1 << (i-1))]);
}
}
}
int getlcp(int l, int r){
if (r < l) swap(l, r);
int x = 31 - __builtin_clz(r-l);
return min(lcp[x][l], lcp[x][r - (1 << x)]);
}
void buildrmq(){
for (int i = 0; i < sz; i++) rmq[0][i] = a[i];
for (int i = 1; i < lg; i++){
for (int j = 0; j + (1 << i) <= sz; j++){
rmq[i][j] = max(rmq[i-1][j], rmq[i-1][j + (1 << (i-1))]);
}
}
}
int getmax(int l, int r){
r++;
int x = 31 - __builtin_clz(r-l);
return max(rmq[x][l], rmq[x][r - (1 << x)]);
}
void solve(){
for (int i = lg-1; ~i; i--){
for (int j = 0; j < sz; j++) a[j] = dp[i][j];
buildrmq();
for (int j = 1; j <= q; j++){
if (getmax(L[j], ptr[j]) < R[j]){
ptr[j] = getmax(L[j], ptr[j]);
ans[j] += (1 << i);
}
}
}
}
int main(){
ios_base::sync_with_stdio(false); cin.tie(0);
cin >> n >> q;
for (int i = 1; i <= n; i++){
string t; cin >> t;
l[i] = s.size();
s += t;
r[i] = s.size();
s.push_back('#');
}
cin >> t;
sz = t.size();
l[0] = s.size();
s += t;
r[0] = s.size();
s.push_back('#');
sufarr(s);
buildlcp(s);
for (int i = 1; i <= n; i++){
st.push_back(rnk[l[i]]);
}
sort(all(st));
for (int i = 0; i < sz; i++){
int ptr = lower_bound(all(st), rnk[l[0] + i]) - st.begin();
if (ptr < st.size()) dp[0][i] = max(dp[0][i], min(sz-i, getlcp(rnk[l[0] + i], st[ptr])));
ptr--;
if (ptr >= 0) dp[0][i] = max(dp[0][i], min(sz-i, getlcp(st[ptr], rnk[l[0] + i])));
dp[0][i] += i;
}
for (int i = 1; i < lg; i++){
for (int j = 0; j < sz; j++) a[j] = dp[i-1][j];
buildrmq();
for (int j = 0; j < sz; j++){
if (dp[i-1][j] == sz){
dp[i][j] = sz;
}
else dp[i][j] = getmax(j, dp[i-1][j]);
}
}
for (int i = 1; i <= q; i++){
cin >> L[i] >> R[i];
ptr[i] = L[i];
}
solve();
for (int i = 1; i <= q; i++){
cout << (getmax(L[i], ptr[i]) < R[i]? -1: ans[i] + 1) << '\n';
}
return 0;
}
