#include <bits/stdc++.h>
//#define DEBUG 1106
#define int long long
#define ll long long
#define ld long double
#define pb emplace_back
#define p_q priority_queue
#define m_p make_pair
#define pii pair<int,int>
#define endl '\n'
#define INIT ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define FOR(i,a,b) for(int i = a; i <= b; i++)
#define forn(i,n) for (int i = 0; i < n; i++)
#define forn1(i,n) for (int i = 1; i <= n; i++)
#define all(x) x.begin(),x.end()
#define ft first
#define sd second
#define lowbit(x) (x&(-x))
#define chmax(x,y) x=max(x,y)
#define chmin(x,y) x=min(x,y)
#ifdef DEBUG
#define debug(x) cout << #x << ": " << x << endl;
#else
#define debug(x) 1106;
#endif
using namespace std;
const int N = 1e6+5;
const int M = 2005;
const int inf = 1e9;
const int INF = 1e18;
const int MOD = 1e9+7;
int a[N];
signed main() {
INIT
#ifdef DEBUG
freopen("input.txt", "r", stdin);
#endif
///////////
int n, q;
cin >> n >> q;
forn(i,n) cin >> a[i];
forn(i,q) {
int x, y;
cin >> x >> y;
x--, y--;
int lo = 0;
int hi = y-x+1;
int ans = -1;
while (lo<=hi) {
int mid = (lo+hi)/2;
int t = 0;
for(int i = x; i <= y; i++) {
if(a[i]>=mid) t++;
}
if(t>=mid) {
ans = mid;
lo = mid+1;
} else {
//ans = mid;
hi = mid-1;
}
//cout << "|| t: " << t << ", mid: " << mid << ", lo: " << lo << ", hi: " << hi << endl;
}
cout << ans << endl;
}
}
