#include <iostream>
#include <fstream>
using namespace std;
ifstream f ("fact.in");
ofstream g ("fact.out");
int cifre_zero (int a)
{
    int nr=0;
    while (a%10==0)
    {
        nr++;
        a/=10;
    }
    return nr;
}
int factorial (int a)
{
    int factorial=1;
    for (int i=1;i<=a;i++)
        factorial*=i;
return factorial;

}

int main()
{int N,P;
f>>P;

if (P==0)
    N=1;
else
    while (cifre_zero(factorial(N))!=0)
        N++;
g<<N;

    return 0;
}