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 $$-10^{6} \leq a, b \leq 10^{6} $$
. 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

题目翻译：

计算a+b且以标准输出–每三个为一组（除非少于四个数）

输入规范：

每个输入文件包含一个测试例子，每个例子包含一对整数a和b，且$$ -10^{6} \leq a, b \leq 10^{6} $$。数字以空格分隔

输出规范：

对于每个测试例子，你应该输出a和b的和在一行，且和必须用标准模式输出

示例代码

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#include <iostream>
using namespace std;
int main() {
    int a, b;
    cin >> a >> b;
    //将a+b转成string
    string s = to_string(a + b);
    int len = s.length();
    for (int i = 0; i < len; i++) {
        cout << s[i];
        //遇到负号跳过
        if (s[i] == '-') 
            continue;
        //每三位一输出
        if ((i + 1) % 3 == len % 3 && i != len - 1) 
            cout << ",";
    }
    return 0;
}