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

/**************************************************************
	Problem: 1057
	User: admin
	Language: C++
	Result: Accepted
	Time:19 ms
	Memory:2072 kb
****************************************************************/