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 C (judge verdict: Accepted)

#include <stdio.h>
 
int main()
{
    int a, b, c, n, i, min, pre, cur;
 
    scanf("%d", &n);
 
    scanf("%d", &min);
    scanf("%d", &pre);
 
    a = pre - min;
    if (min > pre) min = pre;
 
    for (i = 2; i < n; i++)
    {
        scanf("%d", &cur);
        b = cur - pre;
        c = cur - min;
 
        if (b > c) { if (a < b) a = b; }
        else if (a < c) a = c;
 
        if (min > cur) min = cur;
 
        pre = cur;
    }
 
    printf("%d\n", a);
    return 0;
}