fn sum(arr: &[i32]) -> i32 {
    let mut sum = 0;
    for i in 0..arr.len() {
        sum += arr[i];
    }
    sum
}

fn main() {
    let arr = [4, 6, 8, 9, 11];
    let res = sum(&arr);
    println!("sum is {}", res);
    println!("arr is {:?}", arr);
}