Function exact_stamp_range_index 

pub fn exact_stamp_range_index(
    bases: &[i64],
    lasts: &[i64],
    target_base: i64,
    target_last: i64,
) -> Option<usize>

Find the first range with both exact inclusive boundaries.

bases and lasts must have equal lengths.

A lasts shorter than bases breaks the precondition and the answer is unspecified; equal lengths are a caller precondition, not a runtime check.