pat-1001 A+B Format

1001:将两数之和转换成3位一逗号

Sample Input
-1000000 9
Sample Output
-999,991

#include<iostream>
using namespace std;
#include<stdio.h>

void format(int num)
{
	if(num>=1000)
	{
		format(num/1000);
		printf(",%03d",num%1000);
	}		
	else
	{
		cout<<num;
	}
}

int main()
{
	int a;
	int b;
	int sum;

	cin>>a;
	cin>>b;
	sum=a+b;

	if(sum<0)
	{
		cout<<"-";
		sum = -sum;
	}
	format(sum);

}