#include <bits/stdc++.h>
using namespace std;
template <class X>
X gcd(X a, X b) {
  return b == 0 ? a : gcd(b, a % b);
}
long long ans;
int main() {
  int T;
  T = 1;
  while (T--) {
    int n;
    ans = 0;
    scanf("%d", &n);
    ans = 0;
    for (int i = 1; i <= n; ++i) {
      long long t;
      scanf("%I64d", &t);
      ans = ans + i * (t - 1) + 1;
    }
    printf("%I64d\n", ans);
  }
  return 0;
}
