#include <fstream>
using namespace std;

ifstream cin("secv011.in");
ofstream cout("secv011.out");

const int nax = 3000005;

int n;
int f[nax];

int main() {
    cin >> n;
    f[n] = 1;
    int pre = 0;

    long long answer = 0;
    for (int i = 1; i <= n; i++) {
        int x;
        cin >> x;
        pre += x;
        answer += f[2 * i - 3 * pre + n];
        f[2 * i - 3 * pre + n]++;
    }

    cout << answer << '\n';
    return 0;
}