#include <iostream>
using namespace std;

int main() {
    int n;
    cin >> n;
    int niza[n];
    int prefix_sum[n];
    int sum = 0;
    for(int i = 0; i < n; i++) {
        cin >> niza[i];
        sum += niza[i];
        prefix_sum[i] = sum;
    }
    for(int i = 0; i < n; i++) {
        int leva_sum = 0;
        if(i != 0) {
            leva_sum = prefix_sum[i - 1];
        }
        int desna_sum = prefix_sum[n - 1] - prefix_sum[i];
        if(leva_sum == desna_sum) {
            cout << i + 1 << endl;
            return 0;
        }
    }
    cout << -1 << endl;
    
    return 0;
}