如题，注释出为错误建边

for(int i=0;i<m;i++){
        int a,x,b,y;
        cin>>a>>x>>b>>y;
        a=2*a-1;    b=2*b-1;
//        G[a+x].push_back(b+(y^1));
//        G[b+y].push_back(a+(x^1));
        G[b+(y^1)].push_back(a+x);
        G[a+(x^1)].push_back(b+y);
    }