#include <bits/stdc++.h>
using namespace std;
const int N = int(3e4 + 5);
const int INF = 1e9 + 7;
int n, a[N];
long long ans = 0, c[N];
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; ++i) {
    int x;
    scanf("%d", &x);
    ans += (1ll * x - 1) * (i - 1ll) + x;
  }
  printf("%I64d", ans);
  return 0;
}
