#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:16777216")
using namespace std;
template <typename T>
inline bool remin(T& c, const T& n) {
  if (c > n) {
    c = n;
    return 1;
  }
  return 0;
}
template <typename T>
inline bool remax(T& c, const T& n) {
  if (c < n) {
    c = n;
    return 1;
  }
  return 0;
}
int main() {
  int n, i, a, sum = 0;
  scanf("%d", &n);
  for (i = 1; i <= n; ++i) {
    scanf("%d", &a);
    sum += a * i;
  }
  printf("%d\n", sum);
  return 0;
}
