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, B, C, K, max, p, q;

   scanf("%d %d %d %d",&A,&B,&C,&K);  
    
   if(A>K){
     max=K;
   }
   else{
     p=K-A;
     if(B>p) 
       max=A;
     else{
       q=p-B;
       if(C>q){
         max=A-q;
       }
       else{
         max=A-C;
       }
     }
   }
   
printf("%d\n",max);
  return 0;
}