#include <bits/stdc++.h>
using namespace std;
const long double sqr5 = sqrt(5), p_ = (1 + sqr5) / 2;
long double tavan(long double a, long long b) {
  return b ? (tavan(a * a, b >> 1) * (b & 1 ? a : 1)) : 1;
}
long double fib(long long x) {
  return (tavan(p_, x) - tavan(1 - p_, x)) / sqr5;
}
long long gcd(long long a, long long b) {
  return (a < b) ? gcd(b, a) : ((a % b == 0) ? b : gcd(b, a % b));
}
bool isprime(long long x) {
  for (long long i = 2; i <= sqrt(x); i++)
    if (!(x % i)) return false;
  return true;
}
ifstream fin("input.txt");
ofstream fout("output.txt");
long long n, a[(1100)], ans, sum;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n;
  for (int i = 0; i < n; i++) cin >> a[i];
  ans = a[n - 1];
  sum = a[n - 1] - 1;
  for (int i = n - 2; i >= 0; i--) {
    ans += a[i] + sum;
    sum += a[i] - 1;
  }
  cout << ans;
  return 0;
}
