#include <bits/stdc++.h>
using namespace std;
unsigned long long A[100], B[100];
int main() {
  int n;
  cin >> n;
  unsigned long long m;
  cin >> m;
  A[99] = m;
  for (int i = 99; i > 0; i--) {
    if (A[i] > 9) {
      A[i - 1] += A[i] / 10;
      A[i] = A[i] % 10;
    }
  }
  for (int i = 2; i <= n; i++) {
    for (int j = 0; j < 100; j++) {
      B[j] = 0;
    }
    cin >> m;
    B[99] = (m - 1) * i + 1;
    for (int j = 99; j > 0; j--) {
      if (B[j] > 9) {
        B[j - 1] += B[j] / 10;
        B[j] = B[j] % 10;
      }
    }
    for (int j = 99; j > 0; j--) {
      A[j] = A[j] + B[j];
      if (A[j] > 9) {
        A[j - 1] += A[j] / 10;
        A[j] = A[j] % 10;
      }
    }
  }
  int i = 0;
  while (!A[i]) {
    i++;
  }
  for (int j = i; j < 100; j++) {
    cout << A[j];
  }
  return 0;
}
