#include <bits/stdc++.h>
using namespace std;
long long i, j, a[111111], b, c, s, x, y, z, t, wair, w, n, m, k, l, a1, b1, c1,
    a2, b2, c2, d1, d2, d3;
vector<double> p, q, r, p1, q1, r1, pp;
int main() {
  cin >> n;
  for (i = 0; i < n; i++) cin >> a[i];
  s = a[0];
  for (i = 1; i < n; i++) {
    s += (i + 1) * (a[i] - 1) + 1;
  }
  cout << s;
  return 0;
}
