fn main() {
    println!("Hello, world!");
}


struct Solution {}

impl Solution {
    pub fn find_duplicate(nums: Vec<i32>) -> i32 {
        for i in 0..nums.len()-1 {
            if nums[i+1..nums.len()].contains(&nums[i]) {
                return nums[i];
            }
        }
        0
    }
}