#include <iostream>
#include <fstream>
using namespace std;
ifstream fin ("fact.in");
ofstream fout ("fact.out");
int p,x=0,i1,i2,c2=0,c5=0,i=2;
int main()
{
    fin>>p;
    while (x<p)
        {
            i1=i;
            i2=i;
            while (i1%2==0 && i1!=0)
                {
                    c2++;
                    i1=i1/2;
                }
            while (i2%5==0 &&i2!=0)
                {
                    c5++;
                    i2=i2/5;
                }
            if (c2<c5) x=c2;
                else x=c5;
            i++;
        }
    fout<<i-1;
    return 0;
}