PAT

#include<iostream>  
#include<cmath>  
using namespace std;  
int main(){  
    long a,b,c;  
    int i,flag;  
    bool is_positive;  
    char result[9];  
   
    while(cin>>a>>b)  
    {  
        c = a+b;  
        if( c>0 )   
            is_positive = true;  
        else  
            is_positive = false;  
       
        flag = 0;         
        if(abs(c) >= 1000){  
            c = abs(c);  //取绝对值  
            for( i=0; c>0; i++){  
                result[i] = c%10 + ‘0‘;  //数字转换成字符  
                c = c/10;  
                if(flag == 2 && c != 0 )     
                {  
                    i++;  
                    result[i] = ‘,‘;   //每三个加一个逗号    
                    flag = 0;  
                }  
                else 
                    flag++;               
            }  
            if( !is_positive )  //结果为负数时  
            {  
                result[i] = ‘-‘;  
                cout<<result[i];  
            }  
   
            i--;  //i指向第一个数字  
            for(; i>=0; i--){  
                cout<<result[i];  
            }                     
            cout<<endl;  
        }  
        else 
        {  
            cout<<c<<endl;  
        }  
    }  
    return 0;  
}