#include <bits/stdc++.h>
using integer = unsigned long long;
template <typename T>
std::istream& operator>>(std::istream& input, std::vector<T>& v) {
  for (T& a : v) input >> a;
  return input;
}
void answer(integer v) { std::cout << v << '\n'; }
void solve(const std::vector<unsigned>& a) {
  const size_t n = a.size();
  integer k = 0;
  for (size_t i = 0; i < n; ++i) k += (a[i] - 1) * integer(i + 1) + 1;
  answer(k);
}
int main() {
  size_t n;
  std::cin >> n;
  std::vector<unsigned> a(n);
  std::cin >> a;
  solve(a);
  return 0;
}
