#include<stdio.h>
int putere(int i){
	int v,k;
	v=i;k=0;
	while (v%5==0){
		k=k+1;
		v=v/5;
	}
	return k;
}
int main(){
	int s,i,p;
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	scanf("%d ",&p);
	s=0;i=0;
	if (p==0)
		printf("1\n");
	while(s<p){
		i=i+5;
		s+=putere(i);
	}
	//if (s-putere(i)<p)
		//printf("-1\n");
	//else 
	printf("%d\n",i);
	return 0;
}