Editorial for DMOPC '14 Contest 2 P4 - Deforestation - Olympiads Online Judge

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 $P[i]$ $P [i]$ be the sum of all masses from element $1$ $1$ to element $i$ $i$ . The sum of all masses from $i$ $i$ to $j$ $j$ can be expressed as $P[j]-P[i-1]$ $P [j] - P [i - 1]$ . 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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