#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    ifstream fin("fact.in");
    ofstream fout("fact.out");
    int i=2, p, n, s=0, l;
    fin>>p;
    if(p==0) fout<<1;
    else
    {
        for(l=5; l<=4*p; l*=5)
            s+=(4*p)/l;
        i=4*p+1;
        while(s<p)
        {
            n=i; l=0;
            while(n%5==0)
            {n/=5; l++;}
            s+=l;
            i++;
        }
        if(s==p) fout<<i-1;
        else fout<<-1;
    }
    return 0;
}