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>

#define TIME_MIN 2
#define TIME_MAX 200000
#define VALUE_MIN 1
#define VALUE_MAX 1000000000

int get_int(int *p_num, int min, int max);
int judge_constraint(int test_num, int min, int max);
int max_profit(int size);

int main(void)
{
    int time_cnt;
    
    if(get_int(&time_cnt, TIME_MIN, TIME_MAX))
    {
        return -1;
    }

    printf("%d\n", max_profit(time_cnt));
    
    return 0;
}

int max_profit(int size)
{
    int min;
    int max;
    int current;
    int i;
    
    /* init  */
    if(get_int(&current, VALUE_MIN, VALUE_MAX))
    {
        return -1;
    }
    min = current;
    max = VALUE_MAX * -1;
    
    /* calc */
    for(i = 1; i < size; i++)
    {
        if(get_int(&current, VALUE_MIN, VALUE_MAX))
        {
            return -1;
        }
        if(max < current - min)
        {
            max = current - min;
        }
        if(min > current)
        {
            min = current;
        }
    }
    
    
    return max;
}

int get_int(int *p_num, int min, int max)
{
	scanf("%d", p_num);
	
	if(judge_constraint(*p_num, min, max) == -1)
    {
        return -1;
    }
	
	return 0;
}
int judge_constraint(int test_num, int min, int max)
{
    if(test_num < min || test_num > max)
    {
        return -1;
    }
    
    return 0;
}