/in/foo.c: In function 'main':
/in/foo.c:6:6: warning: unused variable 'a' [-Wunused-variable]
  int a[2];//a[0]  a[1]
      ^
/in/foo.c:5:12: warning: unused variable 'd' [-Wunused-variable]
  int n,b,c,d;
            ^