Chefina and Swap

CodeChefRating 1735Open on judge ↗

You are given a positive integer $N$. Consider the sequence $S = (1, 2, \ldots, N)$. You should choose two elements of this sequence and swap them. A swap is *nice* if there is an integer $M$ ($1 \le M \lt N$) such that the sum of the first $M$ elements of the resulting sequence is equal to the sum of its last $N-M$ elements. Find the number of nice swaps. ### Input - The first line of the

HINT LADDERno hints yet

L1 Observation

L2 Technique

L3 Approach

L4 Pseudo-code

🔒

L5 Full solution

L5 unlocks only if you insist twice

solution.cppC++17

CodeSearch Tutor

Hints, not spoilers — it won’t hand over the full solution unless you insist.

voice by Sarvam AI