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

#define rd(v) long 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];

int main(){
	char*mmap();
	char*rp=mmap(0l,1l<<25,1,2,0,0ll);
	rd(n);
	kp[1]=1;
	ulong s=0;
	rrep(i,n){
		rd(a);
		s+=a;
		ulong q=(a>>6)+1;
		ulong r=a&63;
		if(r){
			rrep(j,(s>>6)+2-q){
				kp[j+q]^=kp[j+1]<<r|kp[j]>>64-r;
			}
		}
		else{
			rrep(j,(s>>6)+2-q){
				kp[j+q]^=kp[j+1];
			}
		}
	}
	ulong z=0;
	for(ulong k=s;k;--k){
		if(kp[(k>>6)+1]&1l<<k){
			z^=k;
		}
	}
	char wbuf[64],*wp=wbuf+sizeof wbuf;
	wt(z);
	write(1,wp,wbuf+sizeof wbuf-wp);
	_exit(0);
}