countSumOfTwoRepresentations
Given integers n, l and r, find the number of ways to represent n as a sum of two integers A and B such that l ≤ A ≤ B ≤ r.
Example
- For
n = 6,l = 2, andr = 4, the output should becountSumOfTwoRepresentations2(n, l, r) = 2.
There are just two ways to write6asA + B, where2 ≤ A ≤ B ≤ 4:6 = 2 + 4and6 = 3 + 3.
Input/Output
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[execution time limit] 3 seconds
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[input] integer n
A positive integer.
Guaranteed constraints:
5 ≤ n ≤ 109. -
[input] integer l
A positive integer.
Guaranteed constraints:
1 ≤ l ≤ r. -
[input] integer r
A positive integer.
Guaranteed constraints:
l ≤ r ≤ 109,r - l ≤ 106.
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