дерево сумм свер

#include <bits/stdc++.h>
using namespace std;
int n, a[100500], t[500500];
void build(int v, int l, int r) {
    if (l == r) {
        t[v] = a[l];
        return;
    }
    int mid = (l + r) / 2;
    build(v * 2, l, mid);
    build(v * 2 + 1, mid + 1, r);
    t[v] = t[v * 2] + t[v * 2 + 1];
}
int main(){
	freopen("C.in", "r", stdin);
	freopen("C.out", "w", stdout);
	cin >> n;
    for (int i = 1; i <= n; i++)
        cin >> a[i];

	build(1, 1, n);

}