/in/foo.c: In function 'main':
/in/foo.c:47:17: warning: unused variable 'v' [-Wunused-variable]
 int i,j,k,l,g,u,v,head=0,tail=0,xx[10]={1,0,-1,0},yy[10]={0,1,0,-1},used;
                 ^
/in/foo.c: In function 'swp':
/in/foo.c:13:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^
/in/foo.c: In function 'tip':
/in/foo.c:42:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^
/in/foo.c: In function 'untip':
/in/foo.c:45:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^