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: Time Limit Exceeded)

#include<stdio.h>
int main(void){
  int i, j, k;
  int max=-2147483648;
  int a, b, c, sum, x;
  scanf("%d%d%d%d", &a, &b, &c, &sum);
  for( i=0; i <= a; i++){
    for( j=0; j<=b; j++){
      for( k=0; k<=c; k++){
        x=1*i + 0*j + (-1)*k;
        //printf("%d\n", x);
        if(x>max && i+j+k==sum) max=x;
      }
    }
  }
  printf("%d\n", max);
  return 0;
}