#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

char*mmap();
#define RD(v) int v=0;{int _c;while(_c=*rp++-48,_c>=0)v=v*10+_c;}

int a[2000];

int sort1b(b,l,r){
	int ml=l;
	int mr=r;
	while(1){
		while(ml<mr&&!(a[ml]&b)){
			++ml;
		}
		while(ml<mr&&(a[mr-1]&b)){
			--mr;
		}
		if(ml==mr) return ml;
		int t=a[ml];
		a[ml]=a[mr-1];
		a[mr-1]=t;
	}
}

int maxv;

f(p,al,ar,bl,br){
	if(al==ar|bl==br) return;
	if(p<0) {
		if(maxv<(a[al]^a[bl])){
			maxv=a[al]^a[bl];
		}
		return;
	}
	int b=1<<p;
	int am=sort1b(b,al,ar);
	int bm=sort1b(b,bl,br);
	if(am==al&bm==bl|am==ar&bm==br){
		f(p-1,al,ar,bl,br);
	}else{
		f(p-1,al,am,bm,br);
		f(p-1,am,ar,bl,bm);
	}
}

main(){
	char*rp=mmap(0l,11l*2001,1,2,0,0ll);
	RD(n);
	for(int i=0;i<n;++i){
		RD(t); a[i]=t;
	}
	int p=29;
	int m;
	while(p>=0&&(m=sort1b(1<<p,0,n),m==0|m==n))--p;
	if(p>=0) f(p-1,0,m,m,n);
	printf("%d",maxv);
}