#include <stdio.h>
#include <stdlib.h>
//numarul de 5 dintr-un numar
int cnr(int nr)
{
	int num=0;
	while(nr%5==0)
	{
		nr/=5;
		num++;
	}
	return num;
}
int main()
{
 FILE *f=fopen("fact.in","r");
 FILE *g=fopen("fact.out","w");
 unsigned int p;
 fscanf(f,"%d",&p);
 unsigned int i=0;
 unsigned int bz=5;
 if(p<1)bz=1;
 else
 {
 while(i<p)
 {
		i=i+cnr(bz);
		bz+=5;
 }
 bz-=5;
 }
 fclose(f);
 fprintf(g,"%d",bz);
 fclose(g);
  return 0;
}