#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n, sum = 0, i, a[105];
  cin >> n;
  for (i = 0; i < n; i++) {
    cin >> a[i];
  }
  sum = a[0];
  for (i = 1; i < n; i++) {
    sum += i * (a[i] - 1) + a[i];
  }
  cout << sum;
  return 0;
}
