#include <stdio.h>
int v[100];
int main()
{
	int i,j,k,k1=0,k2=0;
	k=1;
	for (i=0; i<13; i++)
	{
		v[i]=k;
		k*=5;
	}
	FILE *in=fopen("factorial.in","r");
	FILE *out=fopen("factorial.out","w");
	fscanf(in,"%d",&k);
	fclose(in);
	
	if (k)
	{
		for (i=5; k2<k; i+=5)
		{
			k1=k2;
			j=1;
			while (i%v[j]==0)
				j++;
			k2=k2+j-1;			
		}
		if (k2>k && k1<k)
			fprintf(out,"-1\n");
		else
			fprintf(out,"%d\n",i-5);
	}
	else
		fprintf(out,"1\n");
	fclose(out);
	
	return 0;
}