#include <stdio.h>
#include <math.h>

int main(int argc, const char * argv[])
{

    long double a=2.0;
    long double b=64.0;
    long double result=powl(a,b)+a;
    printf("a=%Lf, b=%Lf result=%Lf\n",a,b,result);
    return 0;
}

a=2.000000, b=64.000000 result=18446744073709551618.000000