#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e9 + 7;
int64_t int_pow(int64_t base, int64_t exp) {
  int64_t result = 1;
  while (exp) {
    if (exp & 1) result *= base;
    exp /= 2;
    base *= base;
  }
  return result;
}
int64_t gcd(int64_t a, int64_t b) { return b == 0 ? a : gcd(b, a % b); }
int main() {
  ios::sync_with_stdio(0);
  int64_t click = 0, n = 0, a = 0;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> a;
    if (a == 1)
      click++;
    else if (a > 1)
      click += a + (i * (a - 1));
  }
  cout << click;
}
