#include <iostream>
#include <fstream>

using namespace std;

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

int zerouri(int x)
{
    int cnt=0;
    while(x>0)
    {
        cnt+=x/5;
        x/=5;
    }
    return cnt;
}

int main()
{
    long long  p,step,pos;
    fin >> p;
    step=1<<30;
    pos=0;
   while(step>0)
   {
       if(pos+step<=(1<<30) && zerouri(step+pos)<=p)
       {
            pos+=step;
       }
        step=step>>1;
   }
   if(zerouri(pos)==p)
        fout << pos-4;
    else
            fout << -1;

    return 0;
}