/in/foo.c: In function 'main':
/in/foo.c:5:20: error: 'x' undeclared (first use in this function)
     scanf("%d %d",&x, &y);
                    ^
/in/foo.c:5:20: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:5:24: error: 'y' undeclared (first use in this function)
     scanf("%d %d",&x, &y);
                        ^