/in/foo.c: In function 'main':
/in/foo.c:6:23: error: 'z' undeclared (first use in this function)
    6 |         scanf("%d%d",&z,&b);
      |                       ^
/in/foo.c:6:23: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:7:19: error: 'a' undeclared (first use in this function)
    7 |     printf("%d\n",a+b);
      |                   ^
/in/foo.c:5:13: warning: unused variable 's' [-Wunused-variable]
    5 |         int s,b;
      |             ^