Problem:
MathJax.Hub.Config({ tex2jax: { inlineMath: [["$","$"], ["\\(","\\)"]], processEscapes: true }});

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>

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

void profitchange(int *profit,int *max,int *min){
	if(*profit<*max-*min){
		*profit = *max - *min;
	}
}

int getprofit(int n,int A[]){
	int i,profit,max,min;
	profit = A[1]-A[0];
	max=min=A[0];
	for(i=0;i<n;i++){
		if(A[i]<min){
			max=min=A[i];
		}else if(A[i]>max){
			max = A[i];
			profitchange(&profit,&max,&min);
		}else if(A[i]==A[i-1]){
			profitchange(&profit,&max,&min);
		}
	}

	return profit;
}

int main(){
	int n,A[200000];
	read(&n,A);
	printf("%d\n",getprofit(n,A));

	return 0;
}