Problem:
Score : 100 points

Problem Statement

Snuke has N integers: 1,2,\ldots,N.
He will choose K of them and give those to Takahashi.

How many ways are there to choose K consecutive integers?

Constraints

All values in input are integers.

1 \leq K \leq N \leq 50

Input

Input is given from Standard Input in the following format:

N K

Output

Print the answer.

Sample Input 1

3 2

Sample Output 1

2

There are two ways to choose two consecutive integers: (1,2) and (2,3).

Sample Input 2

13 3

Sample Output 2

11

Solution in JavaScript (node.js v5.12) (judge verdict: Wrong Answer)

'use strict'

function Main(input) {
  const G = input.split("\n").slice(1)

  let ans = 0
  let startB = 0
  let endA = 0
  let bothAB = 0

  for (let str of G) {
    ans += (str.split("AB")).length - 1
    if (str.substr(0, 1) === "B" && str.substr(-1, 1) === "A") {
      bothAB++
    } else if (str.substr(0, 1) === "B") {
      startB++
    } else if (str.substr(-1, 1) === "A") {
      endA++
    }

    if (bothAB > 0) {
      if (bothAB > 1) {
        bothAB--
        startB++
        endA++
      }
      if ((startB > 0 || endA > 0) && bothAB > 0) {
        bothAB--
        startB++
        endA++
      }
    }

    while (startB > 0 && endA > 0) {
      startB--
      endA--
      ans++
    }
  }
  
  console.log(ans)
}

Main(require("fs").readFileSync("/dev/stdin", "utf8").trim())