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