#include <bits/stdc++.h>
using namespace std;
const int N = 200005;
using ll = long long;
struct TNode {
  int l, r;
  ll v;
} t[N << 2];
inline int lc(int pos) { return pos << 1; }
inline int rc(int pos) { return pos << 1 | 1; }
int a[N], n, m;
ll sum[N], lazy[N << 2];
inline void pushup(int pos) { t[pos].v = max(t[lc(pos)].v, t[rc(pos)].v); }
void build(int pos, int l, int r) {
  t[pos].l = l;
  t[pos].r = r;
  if (l == r) {
    t[pos].v = a[l] - sum[l - 1];
    return;
  }
  int mid = (l + r) >> 1;
  build(lc(pos), l, mid);
  build(rc(pos), mid + 1, r);
  pushup(pos);
}
inline void pushdown(int pos) {
  t[lc(pos)].v += lazy[pos];
  t[rc(pos)].v += lazy[pos];
  lazy[lc(pos)] += lazy[pos];
  lazy[rc(pos)] += lazy[pos];
  lazy[pos] = 0;
}
void modify(int pos, int l, int r, int v) {
  if (t[pos].l == l && t[pos].r == r) {
    t[pos].v += v;
    lazy[pos] += v;
    return;
  }
  int mid = (t[pos].l + t[pos].r) >> 1;
  pushdown(pos);
  if (r <= mid)
    modify(lc(pos), l, r, v);
  else if (l > mid)
    modify(rc(pos), l, r, v);
  else
    modify(lc(pos), l, mid, v), modify(rc(pos), mid + 1, r, v);
  pushup(pos);
}
int query(int pos) {
  if (t[pos].v < 0) return -1;
  if (t[pos].l == t[pos].r) return t[pos].v ? -1 : t[pos].l;
  pushdown(pos);
  int ret = query(lc(pos));
  if (ret == -1) ret = query(rc(pos));
  return ret;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> n >> m;
  for (int i = 1; i <= n; i++) cin >> a[i], sum[i] = sum[i - 1] + a[i];
  build(1, 1, n);
  int t1, t2;
  for (int i = 1; i <= m; i++) {
    cin >> t1 >> t2;
    t2 = t2 - a[t1];
    a[t1] += t2;
    modify(1, t1, t1, t2);
    if (t1 < n) modify(1, t1 + 1, n, -t2);
    cout << query(1) << endl;
  }
  return 0;
}
