local mfl, mce = math.floor, math.ceil local mmi, mma = math.min, math.max local bls, brs = bit.lshift, bit.rshift local SegTree = {} SegTree.updateAll = function(self) for i = self.stagenum - 1, 1, -1 do local cnt = bls(1, i - 1) for j = 1, cnt do self.stage[i][j] = self.func(self.stage[i + 1][j * 2 - 1], self.stage[i + 1][j * 2]) end end end SegTree.create = function(self, n, func, emptyvalue) self.func, self.emptyvalue = func, emptyvalue local stagenum, mul = 1, 1 self.stage = {{}} while mul < n do mul, stagenum = mul * 2, stagenum + 1 self.stage[stagenum] = {} end self.stagenum = stagenum self.left_stage = {} for i = 1, n do local sp, sz = 1, bls(1, stagenum - 1) while(i - 1) % sz ~= 0 do sp, sz = sp + 1, brs(sz, 1) end self.left_stage[i] = sp end self.sz_stage = {} local tmp, sp = 1, stagenum for i = 1, n do if tmp * 2 == i then tmp, sp = tmp * 2, sp - 1 end self.sz_stage[i] = sp end for i = 1, mul do self.stage[stagenum][i] = emptyvalue end self:updateAll() end SegTree.getRange = function(self, left, right) if left == right then return self.stage[self.stagenum][left] end local stagenum = self.stagenum local ret = self.emptyvalue while left <= right do local stage = mma(self.left_stage[left], self.sz_stage[right - left + 1]) local sz = bls(1, stagenum - stage) ret = self.func(ret, self.stage[stage][1 + brs(left - 1, stagenum - stage)]) left = left + sz end return ret end SegTree.update = function(self, idx) for i = self.stagenum - 1, 1, -1 do local dst = brs(idx + 1, 1) local rem = dst * 4 - 1 - idx self.stage[i][dst] = self.func(self.stage[i + 1][idx], self.stage[i + 1][rem]) idx = dst end end SegTree.setValue = function(self, idx, value, silent) self.stage[self.stagenum][idx] = value if not silent then self:update(idx) end end SegTree.lower_bound = function(self, val) local ret, retpos = -1000000007, 0 local stagenum = self.stagenum local stage, l, r = 1, 1, bls(1, stagenum - 1) while true do local sz = bls(1, stagenum - stage) local tmp = self.func(ret, self.stage[stage][mce(l / sz)]) if tmp < val then ret, retpos = tmp, l + sz - 1 if l + sz <= r then stage, l = stage + 1, l + sz else break end else if sz ~= 1 then stage, r = stage + 1, l + sz - 2 else break end end end return retpos + 1 end SegTree.new = function(n, func, emptyvalue) local obj = {} setmetatable(obj, {__index = SegTree}) obj:create(n, func, emptyvalue) return obj end local n = io.read("*n") local inf = 1000000007 local st = SegTree.new(n, mma, inf) local a = {} for i = 1, n do a[i] = io.read("*n") end local leftplus = {} for i = 1, n do local ai = a[i] local pos = st:lower_bound(ai) leftplus[i] = pos if ai < st:getRange(pos, pos) then st:setValue(pos, ai) end end local leftminus = {} for i = 1, n do st:setValue(i, inf, true) end st:updateAll() for i = 1, n do local ai = -a[i] local pos = st:lower_bound(ai) leftminus[i] = pos if ai < st:getRange(pos, pos) then st:setValue(pos, ai) end end local rightplus = {} for i = 1, n do rightplus[i] = 0 st:setValue(i, inf, true) end st:updateAll() for i = n, 1, -1 do local ai = a[i] local pos = st:lower_bound(ai) rightplus[i] = pos if ai < st:getRange(pos, pos) then st:setValue(pos, ai) end end local rightminus = {} for i = 1, n do rightminus[i] = 0 st:setValue(i, inf, true) end st:updateAll() for i = n, 1, -1 do local ai = -a[i] local pos = st:lower_bound(ai) rightminus[i] = pos if ai < st:getRange(pos, pos) then st:setValue(pos, ai) end end local ret = 0 for i = 1, n do -- print(i, leftplus[i], rightplus[i], leftminus[i], rightminus[i]) local v1 = mmi(leftplus[i], rightplus[i]) - 1 local v2 = mmi(leftminus[i], rightminus[i]) - 1 ret = mma(ret, v1, v2) end print(ret)