#include<cstdio>
using namespace std;
int main ()
{
    int N=1,p,j,x=1;
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    scanf("%d",&p);
    if(p==0)
    {
        printf("%d",&x);
    }
    do
    {
        j=N;
        do
        {
            p--;
            j=j/5;
        }while(j%5==0);
        N++;
    }while(p!=0);
    printf("%d",&N);
}