when not declared ATCODER_YULY3HEADER_HPP:
  const ATCODER_YULY3HEADER_HPP* = 1

  import
    algorithm,
    bitops,
    deques,
    heapqueue,
    math,
    macros,
    sets,
    sequtils,
    strformat,
    strutils,
    sugar,
    tables

  proc transLastStmt(n, res, bracketExpr: NimNode): (NimNode, NimNode, NimNode) =
    # Looks for the last statement of the last statement, etc...
    case n.kind
    of nnkIfExpr, nnkIfStmt, nnkTryStmt, nnkCaseStmt:
      result[0] = copyNimTree(n)
      result[1] = copyNimTree(n)
      result[2] = copyNimTree(n)
      for i in ord(n.kind == nnkCaseStmt)..<n.len:
        (result[0][i], result[1][^1], result[2][^1]) = transLastStmt(n[i], res, bracketExpr)
    of nnkStmtList, nnkStmtListExpr, nnkBlockStmt, nnkBlockExpr, nnkWhileStmt,
        nnkForStmt, nnkElifBranch, nnkElse, nnkElifExpr, nnkOfBranch, nnkExceptBranch:
      result[0] = copyNimTree(n)
      result[1] = copyNimTree(n)
      result[2] = copyNimTree(n)
      if n.len >= 1:
        (result[0][^1], result[1][^1], result[2][^1]) = transLastStmt(n[^1],
            res, bracketExpr)
    of nnkTableConstr:
      result[1] = n[0][0]
      result[2] = n[0][1]
      if bracketExpr.len == 1:
        bracketExpr.add([newCall(bindSym"typeof", newEmptyNode()), newCall(
            bindSym"typeof", newEmptyNode())])
      template adder(res, k, v) = res[k] = v
      result[0] = getAst(adder(res, n[0][0], n[0][1]))
    of nnkCurly:
      result[2] = n[0]
      if bracketExpr.len == 1:
        bracketExpr.add(newCall(bindSym"typeof", newEmptyNode()))
      template adder(res, v) = res.incl(v)
      result[0] = getAst(adder(res, n[0]))
    else:
      result[2] = n
      if bracketExpr.len == 1:
        bracketExpr.add(newCall(bindSym"typeof", newEmptyNode()))
      template adder(res, v) = res.add(v)
      result[0] = getAst(adder(res, n))

  macro collect*(init, body: untyped): untyped =
    runnableExamples:
      import sets, tables
      let data = @["bird", "word"]
      ## seq:
      let k = collect(newSeq):
        for i, d in data.pairs:
          if i mod 2 == 0: d
      assert k == @["bird"]
      ## seq with initialSize:
      let x = collect(newSeqOfCap(4)):
        for i, d in data.pairs:
          if i mod 2 == 0: d
      assert x == @["bird"]
      ## HashSet:
      let y = initHashSet.collect:
        for d in data.items: {d}
      assert y == data.toHashSet
      ## Table:
      let z = collect(initTable(2)):
        for i, d in data.pairs: {i: d}
      assert z == {0: "bird", 1: "word"}.toTable

    let res = genSym(nskVar, "collectResult")
    expectKind init, {nnkCall, nnkIdent, nnkSym}
    let bracketExpr = newTree(nnkBracketExpr,
      if init.kind == nnkCall: init[0] else: init)
    let (resBody, keyType, valueType) = transLastStmt(body, res, bracketExpr)
    if bracketExpr.len == 3:
      bracketExpr[1][1] = keyType
      bracketExpr[2][1] = valueType
    else:
      bracketExpr[1][1] = valueType
    let call = newTree(nnkCall, bracketExpr)
    if init.kind == nnkCall:
      for i in 1 ..< init.len:
        call.add init[i]
    result = newTree(nnkStmtListExpr, newVarStmt(res, call), resBody, res)

  proc input*(): string {.inline.} = stdin.readLine
  proc inputs*(): seq[string] {.inline.} = stdin.readLine.split
  proc inputInt*(): int {.inline.} = stdin.readLine.parseInt
  proc inputInts*(): seq[int] {.inline.} = stdin.readLine.split.map(parseInt)
  proc chmax*[T](n: var T, m: T) {.inline.} = n = max(n, m)
  proc chmin*[T](n: var T, m: T) {.inline.} = n = min(n, m)
  proc `%=`*[T: SomeInteger](n: var T, m: T) {.inline.} = n = floorMod(n, m)
  proc `|=`*[T: SomeInteger or bool](n: var T, m: T) {.inline.} = n = n or m
  proc `&=`*[T: SomeInteger or bool](n: var T, m: T) {.inline.} = n = n and m
  proc `^=`*[T: SomeInteger or bool](n: var T, m: T) {.inline.} = n = n xor m
  proc `<<=`*[T: SomeInteger](n: var T, m: T) {.inline.} = n = n shl m
  proc `>>=`*[T: SomeInteger](n: var T, m: T) {.inline.} = n = n shr m

when isMainModule:
  var N, D: int
  (N, D) = inputInts()
  var P, Q: array[1001, int]
  for i in 0..<N:
    (P[i], Q[i]) = inputInts()

  const INF = 10^9

  proc f(t: int): bool =
    var
      bg = (dish: -1, fine: 0)
      sbg = (dish: -1, fine: 0)
    for _ in 0..<D:
      var
        nbg = (dish: -1, fine: -INF)
        nsbg = (dish: -1, fine: -INF)
      for j in 0..<N:

        if bg.dish != j and bg.fine - P[j] >= t:
          let nf = bg.fine - P[j] + Q[j]
          if nbg.fine < nf:
            nsbg = nbg
            nbg = (j, nf)
          elif nsbg.fine < nf:
            nsbg = (j, nf)

        elif sbg.dish != j and sbg.fine - P[j] >= t:
          let nf = sbg.fine - P[j] + Q[j]
          if nbg.fine < nf:
            nsbg = nbg
            nbg = (j, nf)
          elif nsbg.fine < nf:
            nsbg = (j, nf)

      (bg, sbg) = (nbg, nsbg)
    return bg.fine != -INF

  var (ok, ng) = (-INF, 0)
  while ng - ok > 1:
    let med = (ok + ng) shr 1
    if f(med):
      ok = med
    else:
      ng = med
  echo ok