#include <stdio.h>
#include <stdlib.h>
#include <limits.h>




int main()
{

    int p, n, k, m, i, s;
     unsigned long long  f;
     unsigned long long a[100];

    FILE *in = fopen("fact.in", "r");
    FILE *out = fopen("fact.out", "w");

    f=1;
    k=0;
    fscanf(in,"%d", &p);
     for(n=1; n<20; n++)
     {
         f*=n;



             do
             {
                 if(f%10==0)
                 {
                    k++;
                 }

             }
             while(k=!p);
         }




        fprintf(out, "%d", k);


return 0;




}