#include <bits/stdc++.h>
const long long inf = 1e18 + 44;
const int MAX = 3e5 + 9;
const long long int MOD = 1e9 + 7;
const double eps = 1e-1;
double const PI = 3.1415926535897931;
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n;
  cin >> n;
  long long int ans = 0;
  for (long long int i = 1; i <= n; i++) {
    long long int x;
    cin >> x;
    ans = ans + i * (x - 1) + 1;
  }
  cout << ans;
}
