#include <bits/stdc++.h>
using namespace std;
int main(int argc, char **argv) {
  long long int n, c = 0;
  cin >> n;
  vector<long long int> v(n);
  for (int i = 0; i < n; ++i) {
    cin >> v[i];
    if (i == 0)
      c += v[i];
    else
      c += (i + 1) * (v[i] - 1) + 1;
  }
  cout << c;
  return (0);
}
