Problem:
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Maximum Profit

You can obtain profits from foreign exchange margin transactions. For example, if you buy 1000 dollar at a rate of 100 yen per dollar, and sell them at a rate of 108 yen per dollar, you can obtain (108 - 100) × 1000 = 8000 yen.

Write a program which reads values of a currency $R_t$ at a certain time $t$ ($t = 0, 1, 2, ... n-1$), and reports the maximum value of $R_j - R_i$ where $j > i$ .

Input

The first line contains an integer $n$. In the following $n$ lines, $R_t$ ($t = 0, 1, 2, ... n-1$) are given in order.

Output

Print the maximum value in a line.

Constraints

$2 \leq n \leq 200,000$

$1 \leq R_t \leq 10^9$

Sample Input 1

6
5
3
1
3
4
3

Sample Output 1

3

Sample Input 2

3
4
3
2

Sample Output 2

-1

Solution in JAVA (judge verdict: Wrong Answer)

import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.InputMismatchException;
import java.util.List;
import java.util.Optional;

public class Main {
	static StringBuilder out = new StringBuilder();
	// static String ls = System.lineSeparator();
	static final String OK = "OK";
	static final String NG = "NG";
	static final String Possible = "Possible";
	static final String Impossible = "Impossible";
	static FastReader in = new FastReader();

	// static final int INF = Integer.MAX_VALUE - 300000000;

	public static void main(String[] args) throws Exception, IOException {
		Main main = new Main();
		main.run();
	}

	void run() {
		int n = in.nextInt();
		List<Integer> nums = in.nextIntList(n);

		int ans = 0;
		for (int i = 0; i < nums.size() - 1; i++) {
			final int present = nums.get(i);
			List<Integer> afterNums = nums.subList(i + 1, nums.size());
			ans = Math.max(Collections.max(afterNums) - present, ans);
		}
		System.out.println(ans);
	}

	void printExit(Object msg) {
		System.out.println(msg.toString());
		System.exit(0);
	}
}

class FastReader {
	private InputStream in = System.in;
	private byte[] buf = new byte[1024];
	private int charNum;
	private int charLen;
	private StringBuilder sb = new StringBuilder();

	public int read() {
		if (charLen == -1)
			throw new InputMismatchException();
		if (charNum >= charLen) {
			charNum = 0;
			try {
				charLen = in.read(buf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (charLen <= 0)
				return -1;
		}
		return buf[charNum++];
	}

	public String next() {
		int c = read();
		while (isWhitespace(c)) {
			c = read();
		}
		sb.setLength(0);
		do {
			sb.appendCodePoint(c);
			c = read();
		} while (!isWhitespace(c));
		return sb.toString();
	}

	public char[] nextCharArray() {
		return next().toCharArray();
	}

	public int nextInt() {
		return (int) nextLong();
	}

	public int[] nextIntArray(int n) {
		int[] array = new int[n];
		for (int i = 0; i < n; i++)
			array[i] = nextInt();
		return array;
	}

	public List<Integer> nextIntList(int n) {
		Integer[] array = new Integer[n];
		for (int i = 0; i < n; i++)
			array[i] = nextInt();
		return Arrays.asList(array);
	}

	public int[][] nextIntArray2D(int n, int m) {
		int[][] array = new int[n][m];
		for (int i = 0; i < n; i++)
			array[i] = nextIntArray(m);
		return array;
	}

	public List<int[]> nextIntsList(int n, int m) {
		List<int[]> list = new ArrayList<int[]>(n);
		for (int i = 0; i < n; i++)
			list.add(nextIntArray(m));
		return list;
	}

	public long nextLong() {
		int c = read();
		while (isWhitespace(c)) {
			c = read();
		}
		int sgn = 1;
		if (c == '-') {
			sgn = -1;
			c = read();
		}
		long res = 0;
		do {
			if (c < '0' || c > '9')
				throw new InputMismatchException();
			res *= 10;
			res += c - '0';
			c = read();
		} while (!isWhitespace(c));
		return res * sgn;
	}

	public double nextDouble() {
		return Double.parseDouble(next());
	}

	public double[] nextDoubleArray(int n) {
		double[] array = new double[n];
		for (int i = 0; i < n; i++)
			array[i] = nextDouble();
		return array;
	}

	public boolean isWhitespace(int c) {
		return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	}
}