#include <bits/stdc++.h>
int main() {
  long long n;
  scanf("%I64d", &n);
  long long sum = 0;
  for (int i = 1; i <= n; i++) {
    long long num;
    scanf("%I64d", &num);
    sum += (num - 1) * (i - 1) + num;
  }
  printf("%I64d\n", sum);
}
