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segment tree lazy propagation.

struct Value {
    int sum[3];
    void Increase() {
       int t = sum[2];
       for (int i = 1; i < 3; ++i) sum[i] = sum[i - 1];
       sum[0] = t; 
    }
    Value operator + (Value b) {
        Value res;
        for (int i = 0; i < 3; ++i) res.sum[i] = sum[i] + b.sum[i];
        return res;  
    }
};