#include <stdio.h>

int main()
{
	long long s,m;
	long a=0,b=500000000,x=250000000,p;
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	scanf("%ld",&p);
	int y=0;
	while(a<b-1 && y==0){
		s=0;
		m=5;
		while(m<=x){
			s=s+x/m;
			m=m*5;
		}
		if(s>p){
			b=x;
			x=(a+b)/2;
		}
		if(s<p){
			a=x;
			x=(a+b)/2;
		}
		if(s==p){
			y=1;
		}
	}
	if(y==1){
		printf("%ld",x-x%5);
	}else{
		printf("-1");
	}
	return 0;
}