#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,a,b,c,d,e,i=1,h=0;
	cin>>n;
	for(;i<=n;i++){
		a=i%10;
		b=i/10%10;
		c=i/100%10;
		d=i/1000%10;
		e=i/10000;
		if(a==5||b==5||c==5||d==5||e==5){
			if(i%5==0){
				h++;
			}
		}
	}cout<<h;
	
}
/**************************************************************
	Problem: 1057
	User: caiqiaoxi
	Language: C++
	Result: Accepted
	Time:17 ms
	Memory:2072 kb
****************************************************************/