#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; i++)
using namespace std;

typedef long long ll;

int main() {
    ll N, A, ans = 0;
    cin >> N;
    rep(i, N) {
        cin >> A;
        ans += A * (i + 1) * (N - i);
    }
    cout << ans << "\n";
}