#include<fstream>
using namespace std;
fstream f("fact.in",ios::in);
fstream g("fact.out",ios::out);
int numar(long n)
{
    long x,i,y;
    x=1;
    y=0;
    for(i=1;i<=n;i++)
    if(i%2==0 || i%5==0)
    {x=x*i;
    if(x%10==0)
    {
               y++;
               x=x/10;}}
    return y;
    }
int main()
{
    long p,n;
    f>>p;
    if(p==0)
    g<<1;
    else
    {n=1;
    while(numar(n)!=p)
    n++;
    g<<n;}
    return 0;}