#include<bits/stdc++.h>
using namespace std;
int main(){
	int a,b=1,c,d,e=0;
	cin>>a;
	while(b<=a){
		b=d;
		while(d>0){
			c=a%10;
			d=d/10;
			if(c==5){
				if(b%5==0){
					e++;
				}
			}	
		}
	}
	cout<<e;
}
/**************************************************************
	Problem: 1057
	User: panyuchen
	Language: C++
	Result: Time Limit Exceed
****************************************************************/