Solution Review: Big (O) of Nested Loop with Subtraction

fn main(){
    let n = 10; 
    let mut sum = 0; 
    let pie = 3.14; 
    for i in (1..n).rev().step_by(3){
        println!("{}", pie); 
        for j in (0..n).rev(){
            sum += 1; 
        }
    }
    println!("{}",sum);
}