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 <math.h>
#include <stdio.h>
#include <string.h>
long long a, b, c, k, ans = 0;
int main(void) {
    scanf("%lld %lld %lld %lld", &a, &b, &c, &k);
    if (k <= a) {
        printf("%lld\n", a);
    } else {
        for (int i = 0; i < a; i++) {
            ans++;
            k--;
        }
        if (k >= b) {
            for (int i = 0; i < b; i++) {
                k--;
            }
            for (int i = 0; i < k; i++) {
                ans--;
            }
        }
        printf("%lld\n", ans);
    }
}