#include<iostream>
#include<fstream>
using namespace std;
int cati5(int x)
{
    int q=0;
    while(x%5==0)
        q++,x/=5;
    return q;
}
int main()
{
    int p;
    ifstream fin("fact.in");
    fin>>p;
    fin.close();
    int n=5,i,aux;
    while(p>0)
    {
        aux=cati5(n);
        p-=aux;
        n+=5;
    }
    n-=5;
    ofstream fout("fact.out");
    fout<<n;
    fout.close();
    return 0;
}