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: Wrong Answer)

#include <stdio.h>
int main()
{
  long a,b,c,k,i;
  long sum=0;
  int f=0;
  scanf("%ld",&a); scanf("%ld",&b); scanf("%ld",&c); scanf("%ld",&k);
  for(i=0;i<=k;i++){
    if(f==0&&a<=k){
      sum+=a;
      f=1;
      k=k-a;
    }
      if(f==1&&b<=k){
          f=2;
          k=k-b;
      }
    if(f==2&&0<k){
      sum=sum-k;
    }
  }
  printf("%ld",sum);
  return 0;
}