#include <bits/stdc++.h>
using namespace std;
#define task "main"
#define F first
#define S second
#define ii pair<int, int>
#define il pair<int, long long>
#define li pair<long long, int>
#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define FOD(i, b, a) for(int i = (b); i >= (a); --i)
template <class T1, class T2>
bool maximize(T1 &a, T2 b){
if (a < b) {a = b; return true;}
return false;
}
template <class T1, class T2>
bool minimize(T1 &a, T2 b){
if (a > b) {a = b; return true;}
return false;
}
template <class T>
void printArr(T container, string separator = " ", string finish = "\n", ostream &out = cout){
for(auto item: container) out << item << separator;
out << finish;
}
const int MAX_N = (int)2e5 + 5;
int n, q, mx;
int a[MAX_N];
ii queries[MAX_N];
namespace sub1 {
bool check(int val, int l, int r) {
int cnt = 0;
FOR(i, l, r) cnt += a[i] >= val;
return cnt >= val;
}
void solve() {
FOR(i, 1, q) {
int res = -1, l = 1, r = mx;
while (l <= r) {
int mid = (l + r) >> 1;
if (check(mid, queries[i].F, queries[i].S)) l = (res = mid) + 1;
else r = mid - 1;
}
cout << res << "\n";
}
}
}
void solve() {
cin >> n >> q;
FOR(i, 1, n) cin >> a[i];
FOR(i, 1, q) cin >> queries[i].F >> queries[i].S;
mx = *max_element(a + 1, a + n + 1);
if (max(n, q) <= 1000) sub1::solve();
}
int32_t main() {
if (fopen(task".inp", "r")) {
freopen(task".inp", "r", stdin);
freopen(task".out", "w", stdout);
}
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
bool multitest = 0;
int numTest = 1;
if (multitest) cin >> numTest;
while (numTest--) {
solve();
}
return 0;
}
/* Lak lu theo dieu nhac!!!! */
