func_code_string: #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;   }   