RUST: Insert character to -Nth position

fn insert_hyphens_reverse(s: &str, interval: usize) -> String {
    let mut result = String::new();
    let chars: Vec<char> = s.chars().collect();
    let mut count = 0;

    for &c in chars.iter().rev() {
        if count > 0 && count % interval == 0 {
            result.push('-');
        }
        result.push(c);
        count += 1;
    }

    result.chars().rev().collect()
}

// Examples

fn main() {
    let input = "1234567890";
    let interval = 3;
    let result = insert_hyphens_reverse(input, interval);
    println!("Original: {}", input);
    println!("Modified: {}", result);

    let input2 = "abcdefghijklm";
    let interval2 = 4;
    let result2 = insert_hyphens_reverse(input2, interval2);
    println!("Original: {}", input2);
    println!("Modified: {}", result2);
}