/in/foo.c: In function 'main':
/in/foo.c:21:17: warning: implicit declaration of function 'abs' [-Wimplicit-function-declaration]
   printf("%d\n",abs(ans));
                 ^~~
/in/foo.c:6:12: warning: unused variable 'z' [-Wunused-variable]
  int x, y, z;
            ^
/in/foo.c:6:9: warning: unused variable 'y' [-Wunused-variable]
  int x, y, z;
         ^
/in/foo.c:5:12: warning: unused variable 'k' [-Wunused-variable]
  int i, j, k;
            ^