/in/foo.cc:6:8: error: 'string' does not name a type; did you mean 'stdin'?
    6 | static string build(int i,int j){
      |        ^~~~~~
      |        stdin
/in/foo.cc: In function 'int main()':
/in/foo.cc:28:20: error: 'build' was not declared in this scope
   28 |     printf("%s\n", build(1,n).c_str());
      |                    ^~~~~