ATM need help

  #include < stdio.h >

  void main ()

  {

  int w;

  float b;

scanf("%d %f",&w,&b);

if ((w%5==0)&&((b-0.5)>w))

    printf("%.2f",(b-0.5-w));

else

    printf("%.2f",b);
  }

whats wrong in this?