#include <bits/stdc++.h>
using namespace std;
template <class T>
T abs(T x) {
  return x > 0 ? x : (-x);
}
template <class T>
T sqr(T x) {
  return x * x;
}
int main() {
  int n;
  cin >> n;
  vector<long long> v(n);
  for (int i = 0; i < n; ++i) cin >> v[i];
  long long res = 0;
  for (int i = 0; i < ((int)(v).size()); ++i) {
    res += 1LL;
    res += (i + 1LL) * (v[i] - 1LL);
  }
  cout << res << "\n";
  return 0;
}
