fn gradingStudents(grades: &[i32]) -> Vec<i32> {
    grades.iter()
        .map(|&x| {
            let modulo = 5 - (x % 5);
            if x >= 38 && (modulo > 0 && modulo < 3) {
                x + modulo
            } else {
                x
            }
        })
        .collect()
}