VI V(1d5,-1),X(1d5,0);
int root(int a){
	if(V[a]<0) return a;
	int p=V[a], r=root(p);
	V[a]=r; X[a]^=X[p];
	return r;
}
int merge(int r,int c,int y){
	int rr=root(r), rc=root(c);
	if(rr==rc) return X[r]^X[c]^y;
	V[rc]=r; X[rc]=y^X[c];
	return 0;
}

int main(){
	int @N,@M;
	REP(M){
		int @a,@b,@y;
		if(merge(a-1,b-1,y)) printf("-1\n"), return 0;
	}
	rep(i,N) root(i),wt(X[i]);
	return 0;
}