#include<fstream>
#include<iostream>
using namespace std;
int main()
{
 int p,n=0;
 ifstream fin("fact.in");
 fin>>p;
 fin.close();
 ofstream fout("fact.out");
 if(p==0)n=1;
 while(p)
    {
     n+=5;
     p--;
     if(n/25<5)p-=2;
     if(n/125<5)p-=3;
     if(n/625<5)p-=4;
     if(n/3125<5)p-=5;
    }
 if(p<0)n=-1;   
 fout<<n;
 fout.close();
 return 0;
}