Problem:
Score : 200 points

Problem Statement

We have A cards, each of which has an integer 1 written on it. Similarly, we also have B cards with 0s and C cards with -1s.

We will pick up K among these cards. What is the maximum possible sum of the numbers written on the cards chosen?

Constraints

All values in input are integers.

0 \leq A, B, C

1 \leq K \leq A + B + C \leq 2 \times 10^9

Input

Input is given from Standard Input in the following format:

A B C K

Output

Print the maximum possible sum of the numbers written on the cards chosen.

Sample Input 1

2 1 1 3

Sample Output 1

2

Consider picking up two cards with 1s and one card with a 0.
In this case, the sum of the numbers written on the cards is 2, which is the maximum possible value.

Sample Input 2

1 2 3 4

Sample Output 2

0

Sample Input 3

2000000000 0 0 2000000000

Sample Output 3

2000000000

Solution in C (GCC 9.2.1) (judge verdict: Wrong Answer)

#include <stdio.h>

int main(void){
    int a, b, c, k, sum, a_num = 0, b_num = 0, c_num = 0;

    scanf("%d %d %d %d", &a, &b, &c, &k);
    for(int i = 0;i < k; i++){
        if(a_num != a){
            sum += 1;
            a_num++;
        }
        else if(b_num != b){
            b_num++;
        }
        else{
            sum -= 1;
            c_num++;
        }
    }

    printf("%d\n", sum);

    return 0;
}