Calculate a+b and output the sum in standard format -- that is, the digits must be separated into groups of three by commas (unless there are less than four digits).

Input Specification:

Each input file contains one test case. Each case contains a pair of integers a and b where ?10?^6??≤a,b≤10^?6??. The numbers are separated by a space.

Output Specification:

For each test case, you should output the sum of a and b in one line. The sum must be written in the standard format.

Sample Input:

-1000000 9

Sample Output:

-999,991


分析：註意到a,b的範圍可以用int型表示，int可以表示10^9的範圍，一開始想復雜了，其實直接把字符串逆置後，從高位輸出，每輸出3個數字輸出一個逗號就行了。

 1 /**
 2 * Copyright(c)
 3 * All rights reserved.
 
 4 * Author : Mered1th
 5 * Date : 2019-02-24-19.21.16
 6 * Description : A1001
 7 */
 8 #include<cstdio>
 9 #include<cstring>
10 #include<iostream>
11 #include<cmath>
12 #include<algorithm>
13 #include<string>
14 #include<unordered_set>
15 #include<map>
16 #include<vector>
17
 
 #include<set>
18 using namespace std;
19 
20 int main(){
21 #ifdef ONLINE_JUDGE
22 #else
23     freopen("1.txt", "r", stdin);
24 #endif
25     int a,b,c;
26     scanf("%d%d",&a,&b);
27     c=a+b;
28     if(c<0){
29         printf("-");
30         c=-c;
31     }
32     string s=to_string(c);
33     reverse(s.begin(),s.end());
34     int len=s.length();
35     for(int i=len-1;i>=0;i--){
36         if((i+1)%3==0&&i!=len-1&&i>0){
37             printf(",");
38         }
39         printf("%c",s[i]);
40     }
41     return 0;
42 }

1001 A+B Format （20 分）