#include <fstream>

using namespace std;

ifstream cin("fact.in");
ofstream cout("fact.out");

const int CMAX = 5e8+0 , CMIN = 1;
int n;

int nr_zero(int N)
{
    int s=0,p=5;
    while(N>=p)
    {
        s+=N/p;
        p*=5;
    }
    return s;
}

int cautare_binara(int s , int d , int P)
{
    int mid , hai , rezultat = 0;
    while(s<=d)
    {
        mid = (s+d)/2;
        hai = nr_zero(mid);
        if(hai==P)
        {
            rezultat = mid;
            d = mid-1;
        }
        if(hai<P) s = mid+1;
        else d = mid-1;
    }
    return rezultat;
}

int main()
{
    cin >> n;
    cout << cautare_binara(CMIN,CMAX,n);
    return 0;
}