#include <bits/stdc++.h>
using namespace std;
#pragma comment(linker, "/STACK:100000000")
int main() {
  int n;
  scanf("%d", &n);
  long long ans = 0;
  for (int i = 0; i < n; i++) {
    long long a;
    cin >> a;
    ans += (a - 1LL) * (long long)i + a;
  }
  cout << ans << endl;
  return 0;
}
