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

#define rd(v) ulong v=0;{long _c;while(_c=*rp++-48,_c>=0)v=v*10+_c;}
#define wt(v) {ulong _z=v;do*--wp=_z%10+48;while(_z/=10);}
#define rep(v,e) for(long v=0;v<e;++v)
#define rrep(v,e) for(long v=e;v--;)

typedef unsigned long ulong;

#define KPMAX 4000000
ulong kp[KPMAX/64+2];
ulong b[KPMAX/64+2];

void f0(){
	char*mmap();
	char*rp=mmap(0l,1l<<25,1,2,0,0ll);
	rd(n);
	rrep(i,n){
		rd(a);
		while(b[a>>6]&1ul<<a){
			b[a>>6]^=1ul<<a;
			a<<=1;
		}
		b[a>>6]^=1ul<<a;
	}
}

ulong f1(){
	kp[1]=1;
	ulong s=0;
	rep(q,KPMAX/64+2){
		if(b[q]){
			rep(r,64){
				if(b[q]&1ul<<r){
					s+=q<<6|r;
					if(r){
						rrep(j,(s>>6)+1-q){
							kp[j+1+q]^=kp[j+1]<<r|kp[j]>>64-r;
						}
					}
					else{
						rrep(j,(s>>6)+1-q){
							kp[j+1+q]^=kp[j+1];
						}
					}
				}
			}
		}
	}
	return s;
}

ulong f2(ulong s){
	ulong z=0;
	for(ulong k=s;k;--k){
		if(kp[(k>>6)+1]&1l<<k){
			z^=k;
		}
	}
	return z;
}

void f3(ulong z){
	char wbuf[64],*wp=wbuf+sizeof wbuf;
	wt(z);
	write(1,wp,wbuf+sizeof wbuf-wp);
	_exit(0);
}

int main(){
	f0();
	f3(f2(f1()));
}