#include<fstream>
using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
int main()
{
    int n=0,p,zero=0,p5=0,p2=0,n1;
    in>>p;
    if(p==0)
    {
        out<<1;
        return 0;
    }
    while(zero!=p)
    {
        n++;
        n1=n;
        while(n1%2==0)
        {
            n1=n1/2;
            p2++;
        }
        while(n1%5==0)
        {
            n1=n1/5;
            p5++;
        }
        if(p5&&p2)
        {
            zero++;
            p5--;
            p2--;
        }
    }
    out<<n;
    return 0;
}