蒟蒻60分求助!!!

#include <iostream>
using namespace std; 
int main(int argc, char** argv) {
	unsigned long long sum=1,a,b;
	cin>>a>>b;
	for(int i=1;i<=b;i++)
	{
		sum*=a;
	}
	if(sum<10)
	{
		cout<<"00"<<sum<<endl;	
	}
	else if(sum<100)
	{
		cout<<"0"<<sum<<endl;
	}
	else if(sum<1000)
	{
		cout<<sum<<endl;		
	}
	else
	{
		sum=sum%1000;
		cout<<sum<<endl;
	}
	return 0;
}