#include <bits/stdc++.h>
using namespace std;
int main(){
	int a,b,c,d,e,n,i,h=0;
	cin>>n;
	for(i=1;i<=n;i++){
		a=i%10;
		b=i/10%10;
		c=i/100%10;
		d=i/1000%10;
		e=i/10000;
		if(i%5==0&&(a==5||b==5||c==5||d==5||e==5)){
			h++;
		}
	}
	cout<<h;

}

/**************************************************************
	Problem: 1057
	User: 15159808820
	Language: C++
	Result: Accepted
	Time:16 ms
	Memory:2072 kb
****************************************************************/