чего не хватает?
package com.javarush.task.task05.task0532;
import java.util.Scanner;
public class Solution {
public static void main(String[] args) throws Exception {
Scanner scanner = new Scanner(System.in);
int n = scanner.nextInt();
int i;
int max = 0;
if (n > 0) {
for (i = 0; i < n; i++){
int m = scanner.nextInt();
if (max < m) {
max = m;
}
}
}
if (n > 0)
System.out.println(max);
}
}