Есть идеи почему не верно ?
package com.javarush.task.task05.task0532;
import java.io.*;
public class Solution {
public static void main(String[] args) throws Exception {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
int n = Integer.parseInt(reader.readLine());
int maximum = 0;
for (int m = n; m > 0; m--){
int f = Integer.parseInt(reader.readLine());
if (f>maximum){
maximum = f;
}
}
System.out.println(maximum);
}
}