/in/foo.c: In function 'main':
/in/foo.c:3:1: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
 scanf("%d",&a);
 ^~~~~
/in/foo.c:3:1: warning: incompatible implicit declaration of built-in function 'scanf'
/in/foo.c:3:1: note: include '<stdio.h>' or provide a declaration of 'scanf'
/in/foo.c:10:1: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
 printf("Yes");
 ^~~~~~
/in/foo.c:10:1: warning: incompatible implicit declaration of built-in function 'printf'
/in/foo.c:10:1: note: include '<stdio.h>' or provide a declaration of 'printf'
/in/foo.c:12:1: warning: incompatible implicit declaration of built-in function 'printf'
 printf("No");
 ^~~~~~
/in/foo.c:12:1: note: include '<stdio.h>' or provide a declaration of 'printf'