foo.cc: In function 'int main()':
foo.cc:6:9: error: 'cin' was not declared in this scope
    6 |         cin>>a>>b;
      |         ^~~
foo.cc:8:9: error: 'cout' was not declared in this scope
    8 |         cout<<"两数相加="<<c<<endl;
      |         ^~~~
foo.cc:8:31: error: 'endl' was not declared in this scope
    8 |         cout<<"两数相加="<<c<<endl;
      |                               ^~~~

[Hydro](https://hydro.ac)提供评测服务