#include<stdio.h>
long p,s,s2;
int main()
{
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	scanf("%ld",&p);
	if(p>5)
	{
	s=0;
	while (s<=p)
	{
		s2=s2+5;
		if (s2>=25&&s2<125)
			s=s+2;
		else
		if (s2>=125&&s2<625)
			s=s+3;
		else
		if (s2>=625&&s2<390625)
			s=s+4;
		else
		if (s2>=390625&&s2<1953125)
			s=s+5;
		else
		if (s2>=1953125&&s2<9765625)
			s=s+6;
		else
		if (s2>=9765625&&s2<48828125)
			s=s+7;
		else
			s=s+1;
	}
	printf("%ld",s2);
	}
	else
		if (p==0) printf("1");
		else
			printf("%ld",p*5);
}