int dpMinCostColor(vector<int>& a)
{
	int na=a.size();
	// 0: red, 1: blue, 2: green
	int costs[3][na];
	costs[0][0]=cr;
	costs[1][0]=cb;
	costs[2][0]=cg;

	for(int i=1;i<na;i++){
		costs[0][i]=cr + min(costs[1][i-1], costs[2][i-1]);
		costs[1][i]=cb + min(costs[0][i-1], costs[2][i-1]);
		costs[2][i]=cg + min(costs[0][i-1], costs[1][i-1]);
	}

	return min(costs[0][na-1], costs[1][na-1], costs[2][na-1]);
}