#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n;
  cin >> n;
  long long int vet[n];
  for (int i = 0; i < n; ++i) {
    cin >> vet[i];
  }
  long long saida = 0;
  for (int i = n - 1; i >= 0; --i) {
    if (i != n - 1) vet[i]--;
    saida += vet[i] * (i + 1);
  }
  cout << saida << endl;
}
