void muri(){
	wt(0);
	exit(0);
}

char vis[2d5+1];
int ioc[2d5+1];
{
	unionFind u;
	u.walloc(2d5+1,1);
	ll@n;
	ll x=0,y=0,z=0;
	rep(n){
		ll@h,@w;
		vis[h]=1;
		vis[w]=1;
		ioc[h]+=1;
		ioc[w]-=1;
		u(h,w);
		x=h;
	}
	x=u(x);
	rep(i,1,2d5+1){
		if(vis[i]){
			if(u(i)!=x||ioc[i]<-1||ioc[i]>1){
				muri();
			}
			if(ioc[i]==-1){
				if(y&1){
					muri();
				}
				y|=1;
			}
			if(ioc[i]==1){
				if(y&2){
					muri();
				}
				y|=2;
			}
			z+=1;
		}
	}
	wt(y?1:z);
}