c_programming_sum_s

// Su dung vong lap for
// Tinh tong day so S(x, n) = x + 2x + 3x + ... + nx
// VD:  S(1, 2) = 1 + 1.2 = 3
//      S(2, 5) = 2 + 2.2 + 2.3 + 2.4 + 2.5 = 30

int TongS(int x, int n)
{

}

int main()
{

    return 0;
}