#include <fstream>

using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int howmany_5(int n)
{
    int i,p=1,nr=0;
    while (p<=n)
    {
        p=p*5;
        nr=nr+n/p;
    }
    return nr;
}
int n,p,u,mij,sol;
int main()
{
    fin >>n;
    p=1;
    u=1000000;
    while (p<=u)
    {
        mij=(p+u)/2;
        if (howmany_5(mij)==n) {sol=mij;u=mij-1;}
        else if (howmany_5(mij)<n) p=mij+1;
        else u=mij-1;
    }
    fout <<sol;
    return 0;
}