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>
#include <stdlib.h>
#include <string.h>
#define max(a, b) ((a)>(b)?(a):(b))
#define min(a, b) ((a)<(b)?(a):(b))

int main(void){
    int *r;
    int n;
    int maxv;
    int minr;
    int j;
    maxv = -1000000000;
    minr = 1000000000;
    scanf("%d", &n);

    r = (int *)malloc(sizeof(int) * n);
    for (j = 0; j < n; j++){
        scanf("%d", &r[j]);
    }

    for (j = 1; j < n; j++){
        minr = min(minr , r[j - 1]);
        maxv = max(maxv, r[j] - minr);
    }

    printf("%d\n", maxv);

    return 0;
}