#include <iostream>
#include <fstream>
#define nmax 1000
using namespace std;

ifstream f("fact.in");
ofstream g("fact.out");
long p;
long nr;
int rez;

int main()
{
    f>>p;
    if(p==0)
    {
        g<<1;
        return 0;
    }
    int st=0, dr=nmax, c, j;
    while(st<dr)
    {
        c=(st+dr)/2;
        nr=0;
        for(int i=1;i<=c;i++) ///descompunere
        {
            j=i;
            while(j%5==0)j/=5,nr++;
        }

        if(nr==p)
        {
            rez=c;
            dr=c;
        }
        else if(nr>p)dr=c-1;
        else st=c+1;
    }
    g<<rez;
    return 0;
}