#include "stdio.h"
#include "malloc.h"
#include "string.h"

int main()
{
	FILE *f,*g;
	f=fopen("fact.in","r");
	g=fopen("fact.out","w");
	unsigned long int i,x,t;
	fscanf(f,"%ld",&x);
	if(x==0)
		fprintf(g,"%d",1);
	else
	{
		i=0;
		do
		{
			i++;
			t=i;
			x--;
			while((t%5)==0)
			{
				x--;
				t/=5;
			}
		}
		while(x>0);
		if(x)
			fprintf(g,"%d",-1);
		else
			fprintf(g,"%ld",i*5);
	}		
	fclose(g);
	return(0);
	
}