#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");

int abc(int n)
{
    unsigned long long factorial=1;
    for(int i=2;i<=n;i++)
    factorial=factorial*i;
    return factorial;
}
bool verifP(unsigned long long factorial,unsigned long long P )
{
    unsigned long long nr=0,aux=P;
    while(aux!=0)
    {
        if(factorial%10==0)
        nr++;
        factorial/=10;
        aux--;
    }
    if(nr==P)
    return true;
    return false;
}

int main()
{
int N,P,fact,a;
f>>P;
for(int i=1;i > 0;i++)
{
    a = abc(i);
    if(verifP(a,P))
    {
    g<<i;
    break;
    }
}
}