#include <bits/stdc++.h>
using namespace std;
long long num[2000000];
int main() {
  long long n;
  while (cin >> n) {
    long long sum = 0;
    for (long long i = 1; i <= n; i++) {
      cin >> num[i];
      sum += (num[i] - 1) * i;
    }
    sum += n;
    cout << sum << endl;
  }
  return 0;
}
