#include <fstream>

using namespace std;

ifstream f("fact.in");
ofstream g("fact.out");
int sol=-1,p;

int nrcif(long long x)
{
    int k=0,j=5;
    while(j<=x)
    {
        k=k+x/j;
        j*=5;
    }
    return k;
}
void cautbin(long long st, long long dr)
{   int n;
    long long m;
    while (st<=dr)
    {
        m=(st+dr)/2;
        n=nrcif(m);
    if(n<p)
        cautbin(m+1,dr);
    else if(n>p)
            cautbin(st, m-1);
    else
        {
        sol=m;
        cautbin(st,m-1);
        }
    }
}

int main()
{
    f>>p;
    long long st=1, dr=1000;
    cautbin(st,dr);
    g<<sol;
    return 0;
}