#include <stdio.h>
int main()
{
	int k,k1,k2,kt,f=0,ko;
	
	FILE *in=fopen("fact.in","r");
	FILE *out=fopen("fact.out","w");
	fscanf(in,"%d",&k);
	fclose(in);
	
	if (k)
	{
		k1=k;
		while (f==0)
		{
			kt=k1;	k2=0;
			while (kt)
			{
				k2+=kt/5;	kt/=5;
			}
			
			k2=k1+k2;
			if (k2>k)
				if (k2-k>1)
					k1-=(k2-k)/2;
				else
					k1--;
			if (k2==k)
				f=1;
			if (k2<k)
				if (k-k2>1)
					k1-=(k2-k)/2;
				else
					k1++;
			if (k1==k)
				f=-1;
		}
		
		if (f==1)
			fprintf(out,"%d\n",k1*5);
		else
			fprintf(out,"-1\n");
	}
	else
		fprintf(out,"1\n");
	fclose(out);
	
	return 0;
}