#include <fstream>

using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int numarare(int n)
{
    int p=5,a=0;
    while(p<=n)
    a=a+n/p,p*=5;
    return a;
}
int cautare(int p)
{
    int dr=5*100000000,st=1;
    while(st<=dr)
    {
        int mij=(st+dr)/2;
        if(numarare(mij)>=p)
            dr=mij-1;
        else
            st=mij+1;
    }
    return st;

}
int p;
int main()
{
    fin>>p;
    fout<<cautare(p);
    return 0;
}