#pragma GCC optimize("fast-math")
#pragma GCC optimize("unroll-loops")
#pragma GCC optimize("O3")
#pragma GCC target("avx2")
#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
using namespace std;
int n, aib[100005], queries, x, y, v[100005], sol[100005], poz[100005];
vector<pair<int, int> >ans[100005];
int lsb(int x)
{
    return (x & (-x));
}
void update(int poz, int val)
{
    for(; poz >= 0; poz -= lsb(poz))
    {
         aib[poz] = max(aib[poz], val);
    }
}
int query(int poz)
{
    int maxim = -1;
    for(; poz <= 100005; poz += lsb(poz))
    {
        maxim = max(aib[poz], maxim);
    }
    return maxim;
}
struct mo
{
    int st, dr, idx;
    bool operator <(const mo &ob) const
    {
        return dr < ob.dr;
    }
}q[100005];
ifstream fin("pq.in");
ofstream fout("pq.out");
int32_t main(int argc, char * argv[])
{
    fin >> n >> queries;
    for(int i = 1; i <= n; ++i)
    {
        fin >> v[i];
        aib[i] = -1;
    }
    for(int i = 1; i <= queries; ++i)
    {
        fin >> x >> y;
        q[i].st = x, q[i].dr = y, q[i].idx = i;
        ans[q[i].dr].push_back({q[i].st, i});
    }
    sort(q + 1, q + queries + 1);

    for(int stcur = 1; stcur <= n; ++stcur)
    {
        if(poz[v[stcur]])
        {
        update(poz[v[stcur]], stcur - poz[v[stcur]]);
        }
        poz[v[stcur]] = stcur;
        for(auto e : ans[stcur])
        {
            int nr = e.second;
            int left = e.first;
            sol[nr] = query(left);
        }
    }
    for(int i = 1; i <= queries; ++i)
    {
        fout << sol[i] << '\n';
    }
    return 0;
}