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"stdlib.h"
#include"string.h"
#include"ctype.h"
int main()
{
    long long a,b,c,k;
    scanf("%lld %lld %lld %lld",&a,&b,&c,&k);
    if(a<=k)
    {
        if(b<=k-a)
        {
            printf("%lld",a-k+a+b);
        }
        else
            printf("%lld",a);
    }
    else
        printf("%lld",k);

    return 0;
}