import macros
macro Please(x): untyped = nnkStmtList.newTree()

Please use Nim-ACL
Please use Nim-ACL
Please use Nim-ACL



import macros;macro ImportExpand(s:untyped):untyped = parseStmt($s[2])
import macros
# {.checks: off.}
ImportExpand "cplib/tmpl/citrus.nim" <=== "when not declared CPLIB_TMPL_CITRUS:\n    const CPLIB_TMPL_CITRUS* = 1\n    {.warning[UnusedImport]: off.}\n    {.hint[XDeclaredButNotUsed]: off.}\n    import os\n    import algorithm\n    import sequtils\n    import tables\n    import macros\n    import std/math\n    import sets\n    import strutils\n    import strformat\n    import sugar\n    import streams\n    import deques\n    import bitops\n    import heapqueue\n    const MODINT998244353* = 998244353\n    const MODINT1000000007* = 1000000007\n    const INF* = 100100111\n    const INFL* = int(3300300300300300491)\n    type double* = float64\n    let readNext = iterator(getsChar: bool = false): string {.closure.} =\n        while true:\n            var si: string\n            try: si = stdin.readLine\n            except EOFError: yield \"\"\n            for s in si.split:\n                if getsChar:\n                    for i in 0..<s.len(): yield s[i..i]\n                else:\n                    yield s\n    proc input*(t: typedesc[string]): string = readNext()\n    proc input*(t: typedesc[char]): char = readNext(true)[0]\n    proc input*(t: typedesc[int]): int = readNext().parseInt\n    proc input*(t: typedesc[float]): float = readNext().parseFloat\n    macro input*(t: typedesc, n: varargs[int]): untyped =\n        var repStr = \"\"\n        for arg in n:\n            repStr &= &\"({arg.repr}).newSeqWith \"\n        parseExpr(&\"{repStr}input({t})\")\n    macro input*(ts: varargs[auto]): untyped =\n        var tupStr = \"\"\n        for t in ts:\n            tupStr &= &\"input({t.repr}),\"\n        parseExpr(&\"({tupStr})\")\n    macro input*(n: int, ts: varargs[auto]): untyped =\n        for typ in ts:\n            if typ.typeKind != ntyAnything:\n                error(\"Expected typedesc, got \" & typ.repr, typ)\n        parseExpr(&\"({n.repr}).newSeqWith input({ts.repr})\")\n    proc `fmtprint`*(x: int or string or char): string = return $x\n    proc `fmtprint`*(x: float or float32 or\n            float64): string = return &\"{x:.16f}\"\n    proc `fmtprint`*[T](x: seq[T] or Deque[T] or HashSet[T] or set[\n            T]): string = return x.toSeq.join(\" \")\n    proc `fmtprint`*[T, N](x: array[T, N]): string = return x.toSeq.join(\" \")\n    proc `fmtprint`*[T](x: HeapQueue[T]): string =\n        var q = x\n        while q.len != 0:\n            result &= &\"{q.pop()}\"\n            if q.len != 0: result &= \" \"\n    proc `fmtprint`*[T](x: CountTable[T]): string =\n        result = x.pairs.toSeq.mapIt(&\"{it[0]}: {it[1]}\").join(\" \")\n    proc `fmtprint`*[K, V](x: Table[K, V]): string =\n        result = x.pairs.toSeq.mapIt(&\"{it[0]}: {it[1]}\").join(\" \")\n    proc print*(prop: tuple[f: File, sepc: string, endc: string, flush: bool],\n            args: varargs[string, `fmtprint`]) =\n        for i in 0..<len(args):\n            prop.f.write(&\"{args[i]}\")\n            if i != len(args) - 1: prop.f.write(prop.sepc) else: prop.f.write(prop.endc)\n        if prop.flush: prop.f.flushFile()\n    proc print*(args: varargs[string, `fmtprint`]) = print((f: stdout,\n            sepc: \" \", endc: \"\\n\", flush: false), args)\n    proc inner_debug*(x: auto) = print((f: stderr, sepc: \"\", endc: \"\",\n            flush: true), x)\n    const LOCAL_DEBUG{.booldefine.} = false\n    macro debug*(n: varargs[typed]): untyped =\n        when LOCAL_DEBUG:\n            result = newNimNode(nnkStmtList, n)\n            for i in 0..n.len-1:\n                if n[i].kind == nnkStrLit:\n                    result.add(newCall(\"inner_debug\", n[i]))\n                    result.add(newCall(\"inner_debug\", newStrLitNode(\": \")))\n                    result.add(newCall(\"inner_debug\", n[i]))\n                else:\n                    result.add(newCall(\"inner_debug\", toStrLit(n[i])))\n                    result.add(newCall(\"inner_debug\", newStrLitNode(\": \")))\n                    result.add(newCall(\"inner_debug\", n[i]))\n                if i != n.len-1:\n                    result.add(newCall(\"inner_debug\", newStrLitNode(\", \")))\n                else:\n                    result.add(newCall(\"inner_debug\", newStrLitNode(\"\\n\")))\n        else:\n            return quote do:\n                discard\n    proc `%`*(x: SomeInteger, y: SomeInteger): int = (((x mod y) + y) mod y)\n    proc `//`*(x: int, y: int): int = ((x - (x%y)) div y)\n    proc `^`*(x: int, y: int): int = x xor y\n    proc `&`*(x: int, y: int): int = x and y\n    proc `|`*(x: int, y: int): int = x or y\n    proc `>>`*(x: int, y: int): int = x shr y\n    proc `<<`*(x: int, y: int): int = x shl y\n    proc `%=`*(x: var SomeInteger or int64, y: SomeInteger or\n            int64): void = x = x % y\n    proc `//=`*(x: var int, y: int): void = x = x // y\n    proc `^=`*(x: var int, y: int): void = x = x ^ y\n    proc `&=`*(x: var int, y: int): void = x = x & y\n    proc `|=`*(x: var int, y: int): void = x = x | y\n    proc `>>=`*(x: var int, y: int): void = x = x >> y\n    proc `<<=`*(x: var int, y: int): void = x = x << y\n    proc `[]`*(x: int, n: int): bool = (x and (1 shl n)) != 0\n\n    proc pow*(a, n: int, m = INFL): int =\n        var\n            rev = 1\n            a = a\n            n = n\n        while n > 0:\n            if n % 2 != 0: rev = (rev * a) mod m\n            if n > 1: a = (a * a) mod m\n            n >>= 1\n        return rev\n    proc sqrt*(x: int): int =\n        assert(x >= 0)\n        result = int(sqrt(float64(x)))\n        while result * result > x: result -= 1\n        while (result+1) * (result+1) <= x: result += 1\n    proc chmax*[T](x: var T, y: T): bool = (if x < y: (x = y; return true;\n        ) return false)\n    proc chmin*[T](x: var T, y: T): bool = (if x > y: (x = y; return true;\n        ) return false)\n    proc `max=`*[T](x: var T, y: T) = x = max(x, y)\n    proc `min=`*[T](x: var T, y: T) = x = min(x, y)\n    proc at*(x: char, a = '0'): int = int(x) - int(a)\n    converter tofloat*(n: int): float = float(n)\n    iterator rangeiter*(start: int, ends: int, step: int): int =\n        var i = start\n        if step < 0:\n            while i > ends:\n                yield i\n                i += step\n        elif step > 0:\n            while i < ends:\n                yield i\n                i += step\n    iterator rangeiter*(ends: int): int = (for i in 0..<ends: yield i)\n    iterator rangeiter*(start: int, ends: int): int = (for i in\n            start..<ends: yield i)\n    proc Yes*(b: bool = true): void = print(if b: \"Yes\" else: \"No\")\n    proc No*(b: bool = true): void = Yes(not b)\n    proc YES_upper*(b: bool = true): void = print(if b: \"YES\" else: \"NO\")\n    proc NO_upper*(b: bool = true): void = Yes_upper(not b)\n    const DXY* = [(0, -1), (0, 1), (-1, 0), (1, 0)]\n    const DDXY* = [(1, -1), (1, 0), (1, 1), (0, -1), (0, 1), (-1, -1), (-1, 0),\n            (-1, 1)]\n    macro exit*(statement: untyped): untyped =\n        quote do:\n            `statement`\n            quit()\n    proc vector*[T](d1, : int, default: T = T(0)): seq[T] = newSeqWith(d1, default)\n    proc vv*[T](d1, d2: int, default: T = T(0)): seq[seq[T]] = newSeqWith(d1,\n            newSeqWith(d2, default))\n    proc vvv*[T](d1, d2, d3: int, default: T = T(0)): seq[seq[seq[\n            T]]] = newSeqWith(d1, newSeqWith(d2, newSeqWith(d3, default)))\n    proc vvvv*[T](d1, d2, d3, d4: int, default: T = T(0)): seq[seq[seq[seq[\n            T]]]] = newSeqWith(d1, newSeqWith(d2, newSeqWith(d3, newSeqWith(d4, default))))\n    proc vvvvv*[T](d1, d2, d3, d4, d5: int, default: T = T(0)): seq[seq[seq[seq[\n            seq[T]]]]] = newSeqWith(d1, newSeqWith(d2, newSeqWith(d3,\n            newSeqWith(d4, newSeqWith(d5, default)))))\n    proc vvvvvv*[T](d1, d2, d3, d4, d5, d6: int, default: T = T(0)): seq[seq[\n            seq[seq[seq[seq[T]]]]]] = newSeqWith(d1, newSeqWith(d2, newSeqWith(\n            d3, newSeqWith(d4, newSeqWith(d5, newSeqWith(d6, default))))))\n    discard\n"

ImportExpand "cplib/graph/graph.nim" <=== "when not declared CPLIB_GRAPH_GRAPH:\n    const CPLIB_GRAPH_GRAPH* = 1\n\n    type Graph*[T] = ref object of RootObj\n        edges*: seq[seq[(int, T)]]\n\n    type WeightedDirectedGraph*[T] = ref object of Graph[T]\n    type WeightedUnDirectedGraph*[T] = ref object of Graph[T]\n    type UnWeightedDirectedGraph* = ref object of Graph[int]\n    type UnWeightedUnDirectedGraph* = ref object of Graph[int]\n\n    type GraphTypes* = Graph or WeightedDirectedGraph or WeightedUnDirectedGraph or UnWeightedDirectedGraph or UnWeightedUnDirectedGraph\n\n    proc add_edge_impl[T](g: GraphTypes, u, v: int, cost: T, directed: bool) =\n        g.edges[u].add((v, cost))\n        if not directed: g.edges[v].add((u, cost))\n\n    #WeightedDirectedGraph\n    proc initWeightedDirectedGraph*(N: int, edgetype: typedesc = int): WeightedDirectedGraph[edgetype] =\n        result = WeightedDirectedGraph[edgetype](edges: newSeq[seq[(int, edgetype)]](N))\n    proc add_edge*[T](g: var WeightedDirectedGraph[T], u, v: int, cost: T) =\n        g.add_edge_impl(u, v, cost, true)\n\n    #WeightedUnDirectedGraph\n    proc initWeightedUnDirectedGraph*(N: int, edgetype: typedesc = int): WeightedUnDirectedGraph[edgetype] =\n        result = WeightedUnDirectedGraph[edgetype](edges: newSeq[seq[(int, edgetype)]](N))\n    proc add_edge*[T](g: var WeightedUnDirectedGraph[T], u, v: int, cost: T) =\n        g.add_edge_impl(u, v, cost, false)\n\n    #UnWeightedDirectedGraph\n    proc initUnWeightedDirectedGraph*(N: int): UnWeightedDirectedGraph =\n        result = UnWeightedDirectedGraph(edges: newSeq[seq[(int, int)]](N))\n    proc add_edge*(g: var UnWeightedDirectedGraph, u, v: int) =\n        g.add_edge_impl(u, v, 1, true)\n\n    #UnWeightedUnDirectedGraph\n    proc initUnWeightedUnDirectedGraph*(N: int): UnWeightedUnDirectedGraph =\n        result = UnWeightedUnDirectedGraph(edges: newSeq[seq[(int, int)]](N))\n    proc add_edge*(g: var UnWeightedUnDirectedGraph, u, v: int) =\n        g.add_edge_impl(u, v, 1, false)\n    discard\n"

ImportExpand "cplib/graph/dijkstra.nim" <=== "when not declared CPLIB_GRAPH_DIJKSTRA:\n    #[ import cplib/graph/graph ]#\n    import std/heapqueue\n    import algorithm\n    const CPLIB_GRAPH_DIJKSTRA* = 1\n    proc restore_dijkstra*[T](G: Graph[T], start: int, ZERO: T = 0, INF: T = int(3300300300300300491)): tuple[costs: seq[T], prev: seq[int]] =\n        var\n            queue = initHeapQueue[(T, int)]()\n            costs = newSeq[T](len(G.edges))\n            prev = newseq[int](len(G.edges))\n        costs.fill(INF)\n        prev.fill(-1)\n        queue.push((ZERO, start))\n        costs[start] = ZERO\n        while len(queue) != 0:\n            var (cost, i) = queue.pop()\n            if cost > costs[i]:\n                continue\n            for (j, c) in G.edges[i]:\n                var temp = costs[i] + c\n                if temp < costs[j]:\n                    prev[j] = i\n                    costs[j] = temp\n                    queue.push((temp, j))\n        return (costs, prev)\n    proc dijkstra*[T](G: Graph[T], start: int, ZERO: T = 0, INF: T = int(3300300300300300491)): seq[T] =\n        var costs, _ = restore_dijkstra(G, start, ZERO, INF)\n        return costs\n    proc restore_shortestpath_from_prev*(prev: seq[int], goal: int): seq[int] =\n        var i = goal\n        while i != -1:\n            result.add(i)\n            i = prev[i]\n        result = result.reversed()\n    proc shortest_path*[T](G: Graph[T], start: int, goal: int, ZERO: T = 0, INF: T = int(3300300300300300491)): tuple[path: seq[int], cost: int] =\n        var (costs, prev) = restore_dijkstra(G, start, ZERO, INF)\n        result.path = prev.restore_shortestpath_from_prev(goal)\n        result.cost = costs[goal]\n    discard\n"


var n,m = input(int)
var g = initweighteddirectedgraph(n,int)
for i in 0..<m:
    var u,v = input(int)-1
    g.add_edge(u,v,1)
var inf = INFL // 1000000
var (d1, c1) = restore_dijkstra(g, 0, 0, inf)
var (d2, c2) = restore_dijkstra(g, n-1, 0, inf)
var (d3, c3) = restore_dijkstra(g, n-2, 0, inf)
var ans = d1[n-1] + d2[n-2] + d3[0]
ans.min = d1[n-2] + d3[n-1] + d2[0]
if ans >=  inf:
    print(-1)
else:
    print(ans)