#include<iostream>
#include<fstream>

using namespace std;

ifstream fin("fact.in");
ofstream fout("fact.out");

int calculate(int n)
{
    int sum=0;
    while(n!=0)
    {
               n/=5;
               sum+=n;
    }
    return sum;
}

int main()
{
    int n,temp,i=1;
    fin>>n;
    while(true)
    {
               temp=calculate(i);
               if(temp==n)
               {
                          fout<<i;
                          break;
               }
               if(temp>n)
               {
                         fout<<"-1";
                         break;
               }
               i++;
    }
    return 0;
}