a + b + c 求和

#include <iostream>
int main()
{
    std::cout << "请输入三个数字,以空格分隔，按回车键结束：" << std::endl;
    int a = , b = , c = ;
    std::cin >> a >> b >> c;
    std::cout << a << " + " << b << " + " << c
    << " = "<< a + b + c << std::endl;
    return ;
}