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use std::cmp;

fn bits_helper(n: u64, i: u64) -> u64 {
    if n == 0 {
        i
    } else {
        bits_helper(n / 2, i + 1)
    }
}

/// Number of bits needed to represent a number.
pub fn bits_needed_for(n: u64) -> u64 {
    cmp::max(bits_helper(n - 1, 0), 1)
}