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: Accepted)

#include <stdio.h>

int main() {
    long long a, b, c, k, t = 0;
    scanf("%lld%lld%lld%lld", &a, &b, &c, &k);
    
    if (a >= k) {
        t += k;
        k = 0;
    } else if (a < k && k > 0) {
        t += a;
        k -= a;
    }

    if (b >= k)
        k = 0;
    else if (b < k && k > 0)
        k -= b;
    
    if (c >= k) {
        t -= k;
        k = 0;
    } else if (c < k && k > 0) {
        t -= c;
        k -= c;
    }
    
        
    printf("%lld\n", t);
        
    return 0;
}