#include <bits/stdc++.h>
using namespace std;
int main(){
	int a,b,x,a1,a2,a3,a4,a5,n=0;
	cin>>a;
	for(b=1;b<=a;b++){
		a1=b/10000;
		a2=b%10000/1000;
		a3=b%1000/100;
		a4=b%100/10;
		a5=b%10;
	if(b%5==0){
	if(a1==5||a2==5||a3==5||a4==5||a5==5)	
	n++;}
	}
	cout<<n;
	return 0;
	}
/**************************************************************
	Problem: 1057
	User: fzy001
	Language: C++
	Result: Accepted
	Time:19 ms
	Memory:2072 kb
****************************************************************/