Код работает правильно, валидатор не принимает :(
package com.javarush.task.task05.task0532;
import java.io.BufferedReader;
import java.io.InputStreamReader;
public class Solution {
public static void main(String[] args) throws Exception {
int firstNumber;
int maximum = 0;
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
int n = Integer.parseInt(reader.readLine());
if (n > 0) {
firstNumber = Integer.parseInt(reader.readLine());
maximum = firstNumber;
for (int i = 0; i < n - 1 ; i++) {
int nextNumber = Integer.parseInt(reader.readLine());
if (nextNumber > firstNumber) {
maximum = nextNumber;
} else {
maximum = maximum;
}
}
System.out.println(maximum);
} else {
}
}
}