#include <fstream>
using namespace std;
ifstream fin ("fact.in");
ofstream fout ("fact.out");
int main()
{
    int p,c,k,cn;
    int n;
    fin>>p;
    n=0;
    while (p!=0){
            n+=5;
            k=0;
            cn=n;
            while (cn%5==0) {
                k++;
                cn/=5;
            }
            p-=k;

    }
    if (n==0) {
        fout<<1;
    }
    else {
        fout<<n;
    }
    }