#include <bits/stdc++.h>
using namespace std;
template <class T>
T MIN(T a, T b) {
  return a >= b ? b : a;
}
template <class T>
T MAX(T a, T b) {
  return a >= b ? a : b;
}
int main(void) {
  long long n;
  cin >> n;
  vector<long long> v;
  v.push_back(-1);
  for (long long i = 1; i <= n; i++) {
    long long t;
    cin >> t;
    v.push_back(t);
  }
  long long ans = 0;
  for (long long i = 1; i <= n; i++) {
    if (v[i] == 1)
      ans += v[i];
    else
      ans += (v[i] - 1) * (i - 1) + v[i];
  }
  cout << ans << endl;
  return 0;
}
