数据点 #2 下载下来可过，然而评测机过不了。

#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 3e5 + 5;
int n, q, a[N], rt, cnt;
struct Query{int x, p, id, ans;}b[N];
struct FHQ_Treap{int l, r, k, v, siz, sum;}t[N << 1];
int New (int vv)
{
	t[++ cnt].v = t[cnt].sum = vv;
	t[cnt].k = rand ();
	t[cnt].siz = 1;
	return cnt;
}
void push_up (int x)
{
    t[x].siz = t[t[x].l].siz + t[t[x].r].siz + 1;
    t[x].sum = t[x].v + t[t[x].l].sum + t[t[x].r].sum;
}
void split (int pos, int x, int &l, int &r)
{
	if (! pos)return l = r = 0, void ();
	if (t[pos].v <= x)
	{
		l = pos;
		split (t[l].r, x, t[l].r, r);
	}
	else
	{
		r = pos;
		split (t[r].l, x, l, t[r].l);
	}
	push_up (pos);
}
int merge (int l, int r)
{
	if (! l || ! r)return l | r;
	int pos;
	if (t[l].k <= t[r].k)t[pos = l].r = merge (t[l].r, r);
	else t[pos = r].l = merge (l, t[r].l);
	push_up (pos);
	return pos;
}
void Insert (int val)
{
    int l, r;
    split (rt, val - 1, l, r);
    rt = merge (merge (l, New (val)), r);
}
int Search (int x, int p)
{
    if (! x || p <= 0)
        return 0;
    if (t[t[x].r].sum >= p)
    	return Search (t[x].r, p);
	return Search (t[x].l, p - t[t[x].r].sum - t[x].v) + t[t[x].r].siz + 1;
}
signed main ()
{
    ios::sync_with_stdio (0);
    cin.tie (0);
    cout.tie (0);
    srand (time (0));
    cin >> n >> q;
    for (int i = 1; i <= n; ++ i)
        cin >> a[i];
    for (int i = 1; i <= q; ++ i)
    {
        cin >> b[i].x >> b[i].p;
        b[i].id = i;
    }
    sort (b + 1, b + q + 1, [](Query a, Query b){return a.x < b.x;});
    int j = 1;
    for (int i = 1; i <= n; ++ i)
    {
        Insert (a[i]);
        while (i == b[j].x && j <= q)
        {
            if (t[rt].sum < b[j].p)
                b[j].ans = -1;
            else
                b[j].ans = Search (rt, b[j].p);
            ++ j;
        }
    }
    sort (b + 1, b + q + 1, [](Query a, Query b){return a.id < b.id;});
    for (int i = 1; i <= q; ++ i)
        cout << b[i].ans << '\n';
    return 0;
}