#include<cstdio>
#include<math.h>
int p;


void cit()
{
	scanf("%d",&p);
}



int fact(int x)
{
	int w=0;
	for(int i=5; i<=x; i*=5)
		w+=x/i;
	
	return w;
}



int cautbin(int li, int ls)
{
	int m;
	
	while(li<ls)
	{
		m=(li+ls)>>1;
		
		int i=fact(m);
		
		if(i>p)
			ls=m-1;
		else
			li=m+1;
	}
	
	printf("%d",li-5);
}		


void rez()
{
	if(p==0)
		printf("1");
	cautbin(1,1000000000);
}
	
	
int main()
{
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	
	cit();
	
	rez();
	
	return 0;
}