/in/foo.cc: In function 'int main()':
/in/foo.cc:7:9: warning: unused variable 'a' [-Wunused-variable]
  int n, a, b, c, f = 0;
         ^
/in/foo.cc:7:12: warning: unused variable 'b' [-Wunused-variable]
  int n, a, b, c, f = 0;
            ^
/in/foo.cc:7:15: warning: unused variable 'c' [-Wunused-variable]
  int n, a, b, c, f = 0;
               ^
/in/foo.cc:7:18: warning: unused variable 'f' [-Wunused-variable]
  int n, a, b, c, f = 0;
                  ^