#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int putere2,putere5,x;
int descompunere(int n)
{
    int d=2;
    while(d<8)
    {
        while(n%d==0)
        {
            if(d==2)  putere2++;
            if(d==5) putere5++;
            n/=d;
        }
        d+=3;
    }
}
int main()
{
    f>>x;
    for(int i=1;; ++i)
    {
        descompunere(i);
        if(putere5==x)
        {
            g<<i;
            return 0;
        }
    }
    return 0;
}