#include<stdio.h>
int main()
{unsigned k,c,l,caz;
 long a,b,aux,i,x;
 int p;

FILE *f=fopen("cifre.in","r");
FILE *g=fopen("cifre.out","w");

fscanf(f,"%ld %ld %d %d",&a,&b,&c,&k);

if(a>b) {aux=a;
	 a=b;
	 b=aux;}

caz=0;

for(i=a;i<=b;i++)
{x=i;
 l=0;

 while(x);
 {if(x%0==c) l++;
  x/=10;}

 if(l==k) caz++;

 }

p=caz/(b-a+1);

fprintf(g,"%d",p);

fclose(f);
fclose(g);
return 0;
}