#include <iostream>
#include <fstream>
#include <vector>

int main()
{
    int N, Q, L, R;

    std::ifstream f("pqin.txt");
    std::ofstream g("pqout.txt");
    std::vector<int> vect;
    int nr;

    f >> N >> Q;
    for (int i = 0; i < N; i++) {
        f >> nr;
        vect.push_back(nr);
    }

    for (int i = 0; i < Q; i++) {
        f >> L >> R;
        L = L - 1;
        R = R - 1;
        int max_cost = -1;
        for (int j = L + 1; j <= R; j++) {
            int current_cost = 0;
            if (vect[j] == vect[L]) {
                current_cost = j - L;
                if (current_cost > max_cost)
                    max_cost = current_cost;
                L = j;
            }
        }
        g << max_cost << std::endl;
    }

    f.close();
    g.close();

    return 0;
}