/in/foo.c: In function 'main':
/in/foo.c:14:15: error: 'u' undeclared (first use in this function)
   scanf("%d",&u);
               ^
/in/foo.c:14:15: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:15:15: error: 'v' undeclared (first use in this function)
   scanf("%d",&v);
               ^