public void ConnectExistingBalloons()
		{ /* BEGIN ConnectExistingBalloons*/
		mass_Geometry ();
		if (BallList.size()>0)
			 {
				Balloon B = (Balloon)(BallList.get(0));
				contacts = new int[N][max_n0];
				for (int i=0;i<N;i++) { for (int j=0;j<B.n0;j++) { contacts[i][j] = -10; } }  // no contact
			 }
		else { IJ.log("Cannot initialize the contact detection in population: " + this.id);   }

		topo = new boolean[N][N];
		for (int i = 0; i < N; i++) {
	        for (int j = 0; j < i; j++) {
			topo[i][j] = false;
			if (N < 4 & i!=j) { topo[i][j] = true; }
			}
	        }
			if (N < 4) { for (int i = 0; i < N; i++) { for (int j = 0; j < N; j++) { topo[i][j] = true; } } }
		} /* END ConnectExistingBalloons*/