/in/foo.cc: In function 'int main()':
/in/foo.cc:10:9: error: 's1' was not declared in this scope; did you mean 'y1'?
   10 |         s1=s1+s;
      |         ^~
      |         y1
/in/foo.cc:10:15: error: 's' was not declared in this scope
   10 |         s1=s1+s;
      |               ^
/in/foo.cc:13:15: error: 's' was not declared in this scope
   13 |         cout<<s;
      |               ^