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[4];
   
    int a,b,c,d;
    b=0;
    c=0;
    d=0;
    for(a=0;a<4;a++){
        scanf("%d",&A[a]);

    }
    for(a=0;a<A[3];a++){
        if(b<A[0]){
            c=c+1;
            b=b+1;
        }else{
            if(d<A[1]){
                d=d+1;
            }else{
                c=c-1;
            }
        }

    }
   printf("%d",c);
    
    
    }