class Solution {
public:
    int maxProfit(vector<int>& prices) {
        int k=2;
        auto s=prices.size();
        if(s==0)
            return 0;
        vector<vector<int>> dp(k+1,vector<int>(s,0));

        for(int i=1;i<=k;++i)
        {
            int buy=dp[i-1][0]-prices[0];
            for(int j=1;j<s;++j)
            {
                dp[i][j]=max(dp[i][j-1],prices[j]+buy);
                buy=max(buy,dp[i-1][j]-prices[j]);
            }
        }
        return dp[2][s-1];
    }
};