#include<stdio.h>
int n,p,i;

int nr0(int x)
{
	int nr=0;
	while(x)
		{			
		nr+=x/5;
		x/=5;
		}
	return nr;
}



int caut(int x)
{
	int i,pas=1<<30;
	for(i=0;pas!=0;pas>>=1)
		if(nr0(i+pas)<p)
			i+=pas;
	return i+1;
}	

int main()
{
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	scanf("%d",&p);
	printf("%d",caut(i));
	
	return 0;
	
}