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>

int main(void){
    int n;
    int a[200000];
    
    scanf("%d",&n);
    
    scanf("%d",a);
    for(int i=1;i<n;i++){
        scanf("%d",a+i);
        a[i-1]=a[i]-a[i-1];
    }
    int y=a[0],z=a[0];
    for(int i=0;i<n-2;i++){
        if(z+a[i+1]>a[i+1]){
            z+=a[i+1];
        }else{
            z=a[i+1];
        }
        
        if(z>y){
            y=z;
        }
    }
    
    printf("%d\n",y);
    
    return 0;
    
}