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(void){

    int A = 0;
    int B = 0;
    int C = 0;
    int K = 0;
    int count = 0;
    int sum = 0;
    scanf("%d %d %d %d", &A, &B, &C, &K);

    count = K - A;
    if (count < 0){
        sum += K;

    } else {
        sum += A;
        count -= B;
        if (count > 0){
            sum -= K - A - B;    
        }
    }
    printf("%d\n", sum);

    return 0;
}