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 INIT_LOOP 0
#define SECOND_ELEMENT 1
#define EXIT_SUCCESS 0
#define ELEMENT_MAX_INIT -1000000001

int main( void )
{
	unsigned long usW_Delement_cnt;
	unsigned long usW_Dloop_cnt;
	signed long ulW_Delement;
	signed long ulW_Delement_first;
	signed long ulW_Delement_min;
	signed long slW_Delement_max;

	scanf("%d", &usW_Delement_cnt );									/*????´??????°?????°??????*/
	for( usW_Dloop_cnt = INIT_LOOP; usW_Dloop_cnt < usW_Delement_cnt; usW_Dloop_cnt++){
		scanf("%ld", &ulW_Delement);
		if( usW_Dloop_cnt == INIT_LOOP ){
			ulW_Delement_first = ulW_Delement;
		}
		else{
			/*else???????????????????????§?????\*/
		}

		if( usW_Dloop_cnt == SECOND_ELEMENT ){
			slW_Delement_max = ulW_Delement - ulW_Delement_first;
		}
		else if( slW_Delement_max < ulW_Delement - ulW_Delement_min ){
			slW_Delement_max = ulW_Delement - ulW_Delement_min;
		}
		else{
			/*else?????????????????????????????\*/
		}

		if( usW_Dloop_cnt == INIT_LOOP ){
			ulW_Delement_min = ulW_Delement;
		}
		else if( ulW_Delement_min > ulW_Delement ){
			ulW_Delement_min = ulW_Delement;
		}
		else{
			/*else?????????????????????????????\*/
		}

	}
	printf("%ld\n", slW_Delement_max);
	return EXIT_SUCCESS;
}