## Editorial for DMOPC '14 Contest 2 P4 - Deforestation

Remember to use this editorial

**only**when stuck, and**not to copy-paste code from it**. Please be respectful to the problem author and editorialist.**Submitting an official solution before solving the problem yourself is a bannable offence.**We will use a prefix sum array here. Let be the sum of all masses from element 1 to element . The sum of all masses from to can be expressed as . The preprocessing time is linear and each query takes constant time. Python users having a hard time should try the PyPy interpreter. Fast input and output methods should be used if possible.

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