Problem:
MathJax.Hub.Config({ tex2jax: { inlineMath: [["$","$"], ["\\(","\\)"]], processEscapes: true }});

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 Go (judge verdict: Accepted)

package main

import (
	"bufio"
	"fmt"
	"log"
	"math"
	"os"
	"strconv"
)

func main() {
	prices := readPrices()

	n := len(prices)

	margin := -int(math.Pow(10, 9))
	//minv := prices[0]
	minv := prices[1]

	//for j := 1; j < n; j++ {
	for j := 2; j < n; j++ {
		if prices[j]-minv > margin {
			margin = prices[j] - minv
		}
		if prices[j] < minv {
			minv = prices[j]
		}
	}

	fmt.Println(margin)
}

func readPrices() []int {
	var prices []int

	scanner := bufio.NewScanner(os.Stdin)
	for scanner.Scan() {
		text := scanner.Text()
		if text == "" {
			break
		}
		i, err := strconv.Atoi(text)
		checkErr(err)
		prices = append(prices, i)
	}

	err := scanner.Err()
	checkErr(err)

	return prices
}

func checkErr(e error) {
	if e != nil {
		log.Fatalln(e)
	}
}