#include <bits/stdc++.h>

int ri() {
	int n;
	scanf("%d", &n);
	return n;
}

int main() {
	int n = ri();
	int64_t res = 0;
	for (int i = 0; i < n; i++) res += (int64_t) (i + 1) * (n - i) * ri();
	printf("%" PRId64 "\n", res);
	return 0;
}