//#include <iostream>
#include <fstream>
#include <algorithm>
#include <string>
#include <vector>
#include <queue>
#include <utility>
#define ll long long int
#include <cstdio>
#define first f
#define second s
#define fi(n) for(i=0;i<n;++i)
#define fj(n) for(j=0;j<n;++j)
#define fk(n) for(k=0;k<n;++k)
using namespace std;
ifstream cin("fact.in");
ofstream cout("fact.out");
ll i,j,k,n,P,rasp,aux;
int cinci[] = {1,5,25,125,625,3125,15625,78125,390625,1953125,9765625,48828125,244140625,1220703125};
int main ()
{
ios_base::sync_with_stdio(false);
cin>>P;
for (i=0;rasp<P;i+=25,rasp+=6);
if (rasp-P!=1)
cout<<i-(rasp-P-1)*5<<'\n';
else cout<<-1<<'\n';

    return 0;
}