#include<cstdio>
#include<cmath>
unsigned long n,i,j,v[100000],a,b,max;
int main(){
    FILE*f=fopen("xormax.in","r");
    FILE*g=fopen("xormax.out","w");
	fscanf(f,"%lu",&n);
	for(i=0;i<n;i++) fscanf(f,"%lu",&v[i]);
	for(i=0;i<n;i++){
		for(j=i+1;j<n;j++)
			if((v[i]^v[j])>max){
				max=v[i]^v[j];
				a=v[i];
				b=v[j];
			}
			if((v[j]^v[i])>max){
				max=v[j]^v[i];
				a=v[j];
				b=v[i];
			}
	}
	
	fclose(f);
    fclose(g);
    return 0;
}