/in/foo.c: In function 'main':
/in/foo.c:6:2: error: 'cin' undeclared (first use in this function)
  cin>>n>>d;
  ^~~
/in/foo.c:6:2: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:25:7: warning: implicit declaration of function 'fabs' [-Wimplicit-function-declaration]
    if(fabs(b[i]-b[j])<=d)
       ^~~~
/in/foo.c:25:7: warning: incompatible implicit declaration of built-in function 'fabs'
/in/foo.c:25:7: note: include '<math.h>' or provide a declaration of 'fabs'
/in/foo.c:27:10: warning: implicit declaration of function 'min' [-Wimplicit-function-declaration]
     c[i]=min(c[i],c[j]+1);
          ^~~
/in/foo.c:36:2: error: 'cout' undeclared (first use in this function)
  cout<<c[n];
  ^~~~