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: Time Limit Exceeded)

#include <stdio.h>

int main(void){
    int n;
    scanf("%d", &n);

    int R[n];
    for(int i = 0; i < n; i++){
        scanf("%d", &R[i]);
    }

    int i;
    int j;
    int max = R[1] - R[0];
    for(i = 0; i < n - 1; i++){
        for(j = i + 1; j < n; j++){
            int before_num = R[i];
            int after_num = R[j];
            if (max < after_num - before_num){
                max = after_num - before_num;
            }
        }
    }

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

    return 0;
}