#include<stdio.h>
int main()
{
	long long p,i,j,m,x,nr,ok;
	freopen("factorial.in","r",stdin);
	freopen("factorial.out","w",stdout);
	ok=1;
	scanf("%lld",&p);
	if (p==0) printf("%d",1);
	else{
			for(i=1,j=5*p;i<=j && ok==1;)
										{
											m=(i+j)/2;
											x=m;
											nr=0;
while(x!=0)
{
nr+=x/5;
x/=5;
}
if(nr==p)
{
printf("%lld",m-m%5);
ok=0;
}
else
{
if(nr<p)
i=m+1;
else
j=m-1;
}
}
if(ok==1)
printf("%d",-1);
}
	return 0;
}