Solution Review: Finding the First Unique Integer in an Array

fn find_first_unique(arr: &[i32]) -> i32 {
    let mut is_repeated = false; 
    for i in 0..arr.len(){
        for j in 0..arr.len(){
            if arr[i] == arr[j] && i != j {
                is_repeated = true;
            }
        }
        if is_repeated == false {
            return arr[i];
        }
        is_repeated = false;
    }
    return -1;
}