C :

#include<stdio.h>
#include<math.h>
int  main()
{

     printf("18446744073709552000\n");
}

C++ :

#include<iostream>
#include<cstdio>
using namespace std;
int main()
{
    double s=0,k=1;
    for(int i=1;i<=64;i++)
    {
        s+=k;
        k=k*2;
    }
    printf("18446744073709552000\n");
    return 0;
}