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

char*mmap();

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

main(){
	char*a,*b;
	{
		char*rp=mmap(0l,1l<<25,1,2,0,0ll);
		rd(n);
		a=rp;
		b=rp+n*2;
	}
	long z=1;
	for(long d=0,e;e=*b;d=e){
		b+=2;
		e^=*a;
		a+=2;
		z+=d^e;
	}
	z>>=1;
	char wbuf[64],*wp=wbuf+sizeof wbuf;
	wt(z);
	write(1,wp,wbuf+sizeof wbuf-wp);
	_exit(0);
}