Strange bug in optimizator

#include<iostream>

long long A[10];

int main()
{
    int n;
    std::cin >> n;

    for (int i = 0; i < n; ++i)
        std::cin >> A[i];
    long long sum = 0;
    long long sumpairs = 0;
    for (int i = 0; i < n; ++i)
    {
        sumpairs = sumpairs + i * A[i] - sum;
        sum += A[i];
    }
    long long ans = sum + 2 * sumpairs;
    std::cout << ans << " " << n;
    return 0;
}