/in/foo.c: In function 'main':
/in/foo.c:6:8: error: 'cin' undeclared (first use in this function)
  while(cin >> s){
        ^
/in/foo.c:6:8: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:7:12: error: 'R' undeclared (first use in this function)
   if(s[0]==R)cout << "Paper\n";
            ^
/in/foo.c:7:14: error: 'cout' undeclared (first use in this function)
   if(s[0]==R)cout << "Paper\n";
              ^
/in/foo.c:8:17: error: 'S' undeclared (first use in this function)
   else if(s[0]==S) cout << "Rock\n";
                 ^
/in/foo.c:9:17: error: 'P' undeclared (first use in this function)
   else if(s[0]==P) cout << "Scissors\n";
                 ^
/in/foo.c:11:1: error: expected declaration or statement at end of input
 }
 ^