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 max_p(long *ary, long len){
    int i, j, buf = 0;
    long m = -2000000000;

    for (j=len-1;j>=0;j--){ 
        for(i=j-1;i>=0;i--){
            buf = ary[j]-ary[i];
            if (buf > m) m=buf;
        }
    }
    return m;
}

int main(void){
    long len;
    scanf("%ld", &len);
    long ary[len];
    for(int i=0;i<len;i++) scanf("%ld", &ary[i]);
    printf("%d\n", max_p(ary, len));
    return 0;
}