#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 o[100000];

int f(int m,int a,int b){
	if(m==0||a+1==b) return 0;

	int c=a;
	int d=b;

	l1:;
	while(o[c]&m){
		++c;
		if(c==d) goto l2;
	}
	while(~o[--d]&m){
		if(c==d) goto l2;
	}
	int t=o[c];
	o[c]=o[d];
	o[d]=t;
	goto l1;

	l2:;
	if(c==a||c==b) return f(m>>1,a,b);
	int z0=f(m>>1,a,c);
	int z1=f(m>>1,c,b);
	return m|(z0<=z1?z0:z1);
}

main(){
	char*rp=mmap(0l,1200l<<10,1,2,0,0ll);
	RD(n);
	for(int i=0;i<n;++i){
		RD(x);
		o[i]=x;
	}
	//printf("%d",f(1<<29,0,n));
	int z=f(1<<29,0,n);
	char wbuf[16];
	char*w=wbuf+16;
	while(*--w=z%10+48,z/=10);
	write(1,w,wbuf+16-w);
	_exit(0);
}