I dont get it the reuqirements work and it compiles corectly but it doesn seem to get validated any ideas ?

package com.codegym.task.task05.task0532;
import java.io.*;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Collections;
public class Solution {
public static void main(String[] args) throws Exception {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
ArrayList <Integer> numbers = new ArrayList<Integer>();
int count=0;
int a = 0;
int n=0;
n = Integer.parseInt(reader.readLine());
while (count < n) {
a=Integer.parseInt(reader.readLine());
if (a > 0) {
numbers.add(a);
count++;
}
}
for (int i=0; i < numbers.size(); i++) {
for(int j=i+1; j < numbers.size(); j++) {
if (numbers.get(i) < numbers.get(j) ) {
Collections.swap(numbers, i, j);
}
}
}
if (numbers.get(0) >= 0 )
System.out.println(numbers.get(0));
}
}