#include <algorithm>
#include <cassert>
#include <iostream>
#include <vector>
using namespace std;
using ll = long long;

ll inversion(vector<ll> &vec) {
    ll N = vec.size();
    ll ret = 0;
    for (ll i = 0; i < N; i++) {
        for (ll j = i + 1; j < N; j++) {
            if (vec[i] > vec[j]) {
                ret++;
            }
        }
    }
    return ret;
}

int main() {
    // 何回の入れ替えが必要になるか、は転倒数によって求める
    ll N, Q;
    cin >> N >> Q;
    string S;
    cin >> S;
    vector<ll> l(Q);
    vector<ll> r(Q);
    for (ll i = 0; i < Q; i++) {
        cin >> l[i] >> r[i];
        assert(r[i] - l[i] + 1 <= 10);
    }
    for (ll i = 0; i < Q; i++) {
        string T = S.substr(l[i] - 1, r[i] - l[i] + 1);
        vector<ll> vec(r[i] - l[i] + 1);
        for (ll j = 0; j < r[i] - l[i] + 1; j++) {
            vec[j] = j;
        }
        ll ans = N * N * N + 1;
        do {
            string U = "";
            for (ll j = 0; j < r[i] - l[i] + 1; j++) {
                U += S[l[i] - 1 + vec[j]];
            }
            if (stoll(U) % 8 == 0) {
                ans = min(ans, inversion(vec));
            }
        } while (next_permutation(vec.begin(), vec.end()));

        if (ans == N * N * N + 1) {
            cout << -1 << endl;
        } else {
            cout << ans << endl;
        }
    }
}