#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
long long k,mij,p,nr;
long zero(long long x)
{
    p=5;
    nr=0;
    while(p<=x)
    {
        nr=nr+x/p;
        p=p*5;
    }
    return nr;
}
long long alg(long long l,long long r)
{
    while(l<=r)
    {
        mij=l+(r-l)/2;
        if(zero(mij)==k)
        {
            if(zero(mij-1)<k||mij==l)
            {
                return mij;
            }
            else
            {
                r=mij-1;
            }
        }
        else
        {
            if(zero(mij)<k)
            l=mij+1;
            else
            r=mij-1;
        }
    }
    return -1;
}
int main()
{
    f>>k;
    g<<alg(1,1000000000);
    return 0;
}