#include <fstream>

using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
long long n,k,p,nr0,p2,p5,aux;
int main()
{
    fin>>n;
    k=1;p=1;nr0=0;p2=0;p5=0;
    while(nr0!=n)
    {
        k++;aux=k;
        while(aux%2==0)
        {
            aux=aux/2;
            p2++;
        }
        while(aux%5==0)
        {
            aux=aux/5;
            p5++;
        }
        while(p2>0 && p5>0)
        {
            nr0++;
            p2--;p5--;
        }

    }
    fout<<k;
    return 0;
}