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: Runtime Error)

#include<stdio.h>
#include<stdlib.h>

#define elemof(n) (sizeof(n) / sizeof(*n))

int input(long *lst, size_t size);
int max_index(long *lst, size_t size);
int min_index(long *lst, size_t size);

int main(void){
    long data[200000] = {0};
    long maxVal = -1000000000;
    int n = 0;
    int maxIndex, minIndex;
    int i ,next_i = 0;
    long Ri , Rj = 0;
    long val = 0;

    n = input(data, elemof(data)); /* ???????????????????????? */

    /* ???????????????????°?????????????????????????????????? (?????????) */
    minIndex = min_index(data , n);

    for (i = 0 ; i < n ; i++){
        Ri = data[i];

        next_i = i + 1;
        if (next_i < n){
            if(maxIndex < next_i){
                /* ????????????????????§????????????????????????????????? (?????????) */
                maxIndex = max_index(&data[next_i] , n);
                maxIndex += next_i;
            }
            Rj = data[maxIndex];

            val = Rj - Ri;
            if (maxVal < val){
                maxVal = val;
            }
            
        }

        if (i == minIndex){
            break;
        }
    }

    printf("%ld\n", maxVal);
    return 0;
}

int input(long *lst, size_t size){
    char str[12] ;
    int n = 0;
    int i;
    /* ?????????????????°????????? */
    fgets(str , elemof(str) , stdin);
    n = atoi(str);

    for(i = 0 ; i < n ; i++){
        fgets(str , elemof(str) , stdin);
        if(i < size){
            lst[i] = (int)(atoi(str));
        }
    }
    return n;
}

/* ?????????????????§??????????????????????????????????????? (?????????) */
int max_index(long *lst, size_t size){
    long maxVal = 0;
    int maxIndex = 0;
    int i;
    for(i = 0 ; i < size ; i++){
        if (maxVal < lst[i]){
            maxVal = lst[i];
            maxIndex = i;
        }
    }
    return maxIndex;
}

/* ????????????????°???????????????????????????????????????? (?????????) */
int min_index(long *lst, size_t size){
    long minVal = 1000000000;
    int minIndex = 0;
    int i;
    for(i = 0 ; i < size ; i++){
        if (minVal > lst[i]){
            minVal = lst[i];
            minIndex = i;
        }
    }
    return minIndex;
}