#include <bits/stdc++.h>
using namespace std;
long long rin() {
  long long s = 0;
  bool bj = 0;
  char c = getchar();
  while ((c > '9' || c < '0') && c != '-') c = getchar();
  if (c == '-') bj = 1, c = getchar();
  while (c >= '0' && c <= '9')
    s = (s << 1) + (s << 3) + (c ^ '0'), c = getchar();
  if (bj) return -s;
  return s;
}
int main() {
  long long i, j;
  long long n;
  long long x;
  cin >> n;
  long long ans = 0;
  for (i = 1; i <= n; i++) x = rin(), ans += (x - 1) * i + 1;
  cout << ans;
  return 0;
}
