Calculate how many cubic meters of round HANKING wheat requires a total reward of his prime minister

#include <iostream>
#include <cmath>
using namespace std;
// 计算舍罕王共需要多少立方的麦子赏赐他的宰相
double WheatNum ()
{
	double sum = 0, m3;    
	for (int i = 0; i < 64; i++)    
	{        
		sum = sum + pow(2,i);    
	}    
	m3 = sum / (1.42 * pow(10,8));    
	return m3; 
}
int main()
{    
	cout << WheatNum () << "立方米麦子。" << endl;
}