int N,a[100000],i;
c(int*a,int*b){return*a-*b;}
f(s,l,r,m){
	for(m=l;m<r&&!(a[m]&1<<s);++m);
	if(s<0){
		return 0;
	}
	if(m!=l&&m!=r){
		return 1<<s|(i=fmin(f(s-1,l,m),f(s-1,m,r)));
	}else{
		return f(s-1,l,r);
	}
}
main(){
	for(scanf("%d",&N);~scanf("%d",a+i++););
	qsort(a,N,4,c);
	printf("%d",f(29,0,N));
}