func main() const invalid: int :: lib@intMax var n: int :: cui@inputInt() var a: []int :: #[n]int for i(0, n - 1) do a[i] :: cui@inputInt() end for var lMin: []int :: #[n]int var rMin: []int :: #[n]int block var min: int :: a[0] for i(1, n - 1) do lMin[i] :: min do min :: [min, a[i]].min() end for end block block var min: int :: a[n - 1] for i(n - 2, 0, -1) do rMin[i] :: min do min :: [min, a[i]].min() end for end block var lLow: []int :: #[n]int var rLow: []int :: #[n]int block var set: Set :: #Set do set.ins(a[0]) for i(1, n - 1) var p: Node :: set.lower_bound(a[i]) do lLow[i] :: p =& null ?(-1, p.key) do set.ins(a[i]) end for end block block var set: Set :: #Set do set.ins(a[n - 1]) for i(n - 2, 0, -1) var p: Node :: set.lower_bound(a[i]) do rLow[i] :: p =& null ?(-1, p.key) do set.ins(a[i]) end for end block var ans: int :: invalid for i(1, n - 2) var v: int :: a[i] ; ^ var lm: int :: lMin[i] var rm: int :: rMin[i] if(lm < v & v > rm) do ans :: [ans, lm + v + rm].min() end if ; v var ll: int :: lLow[i] var rl: int :: rLow[i] if(ll > v & v < rl) do ans :: [ans, ll + v + rl].min() end if end for if(ans = invalid) do ans :: -1 end if do cui@print("\{ans}\n") class Node() +var height: int +var key: int +var lst: Node +var rst: Node +*func toStr(): []char ret "\{me.key}" end func +func init(height: int, key: int): Node do me.height :: height do me.key :: key do me.lst :: null do me.rst :: null ret me end func end class func height(t: Node): int if(t =& null) ret 0 else ret t.height end if end func func bias(t: Node): int ret height(t.lst) - height(t.rst) end func func modHeight(t: Node) do t.height :: 1 + lib@max(height(t.lst), height(t.rst)) end func func rotateL(v: Node): Node var u: Node :: v.rst var t: Node :: u.lst do u.lst :: v do v.rst :: t ret u end func func rotateR(u: Node): Node var v: Node :: u.lst var t: Node :: v.rst do v.rst :: u do u.lst :: t ret v end func func rotateLR(t: Node): Node do t.lst :: rotateL(t.lst) ret rotateR(t) end func func rotateRL(t: Node): Node do t.rst :: rotateR(t.rst) ret rotateL(t) end func ; AVL Set class Set() var root: Node var change: bool var lmax: int +func balanceL(t: Node): Node if(!me.change) ret t end if var h: int :: height(t) if(bias(t) = 2) if(bias(t.lst) >= 0) do t :: rotateR(t) else do t :: rotateLR(t) end if else do modHeight(t) end if do me.change :: (h <> height(t)) ret t end func +func balanceR(t: Node): Node if(!me.change) ret t end if var h: int :: height(t) if(bias(t) = -2) if(bias(t.rst) <= 0) do t :: rotateL(t) else do t :: rotateRL(t) end if else do modHeight(t) end if do me.change :: (h <> height(t)) ret t end func +func ins(key: int) do me.root :: me.insSub(me.root, key) end func +func insSub(t: Node, key: int): Node if(t =& null) do me.change :: true ret(#Node).init(1, key) elif(key < t.key) do t.lst :: me.insSub(t.lst, key) ret me.balanceL(t) elif(key > t.key) do t.rst :: me.insSub(t.rst, key) ret me.balanceR(t) else do me.change :: false ret t end if end func +func find(key: int): Node var t: Node :: me.root while loop(t <>& null) if(key < t.key) do t :: t.lst elif(key > t.key) do t :: t.rst else break loop end if end while ret t end func +func lower_bound(key: int): Node var t: Node :: me.root var last: Node while loop(t <>& null) if(key < t.key) if(t.lst =& null) if(t.key >= key) ret t else ret last end if end if do t :: t.lst elif(key > t.key) if(t.rst =& null) if(t.key >= key) ret t else ret last end if end if do t :: t.rst else break loop end if do last :: t end while ret t end func end class end func