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