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>
#include <inttypes.h>

int main(void) {
	int64_t A, B, C, K;
	int64_t answer = 0;
	if (scanf("%" SCNd64 "%" SCNd64 "%" SCNd64 "%" SCNd64, &A, &B, &C, &K) != 4) return 1;
	if (A >= K) {
		answer += K;
		K = 0;
	} else {
		answer = A;
		K -= A;
	}
	if (B >= K) {
		K = 0;
	} else {
		K -= B;
	}
	if (C >= K) {
		answer -= K;
	} else {
		answer -= C;
	}
	printf("%" PRId64 "\n", answer);
	return 0;
}