#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, s, e) for (int i = (s); i < (int)(e); ++i)
#define all(a) (a).begin(),(a).end()

int main() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    
    int N;
    cin >> N;
    ll ans = 0;
    
    rep(ii, 0, N) {
        ll i = ii;
        ll A;
        cin >> A;
        
        ans += A * (i + 1) * (N - i);
    }
    
    cout << ans << '\n';
}