#include <fstream>
#include <cmath>
using namespace std;
long long log5(long long n)
{
    int l=0;
    while(n%5==0)
    {
        n/=5;
        l++;
    }
    return l;
}
ifstream cin("fact.in");
ofstream cout("fact.out");
int main()
{
    long long p,i,c=0;
    cin>>p;
    if(p==0){
    cout<<1;
    return 0;}
    for(i=5;c<p;i+=5)
    {
        c+=log5(i);
        //cout<<log5(i)<<" ";
    }
    cout<<i-5;
    return 0;
}