import java.io.BufferedReader import java.io.InputStream import java.io.InputStreamReader import java.lang.AssertionError import java.util.* import kotlin.collections.HashSet import kotlin.math.abs import kotlin.math.max import kotlin.math.min val MOD = 1_000_000_007 /** * 単調減少 * [l, h) 方式 * @return マッチするものがなかったらl */ inline fun findMax(l: Int, r: Int, f: (Int) -> Boolean): Int { var low = l var high = r + 1 while(high - low > 1) { val m = (low + high) / 2 if (f(m)) low = m else high = m } return low } data class Val(val i: Int, val a: Int) : Comparable { fun max(v: Val) = if (a > v.a) this else v fun min(v: Val) = if (a <= v.a) this else v override fun compareTo(v: Val): Int { if (a != v.a) return a.compareTo(v.a) return i.compareTo(v.i) } } data class Entry(val mx: Val, val mn1: Val, val mn2: Val?) { fun merge(e: Entry): Entry { val mns = HashSet() mns += mn1 if (mn2 != null) mns += mn2 mns += e.mn1 if (e.mn2 != null) mns += e.mn2 val sort = mns.toMutableList() sort.sort() // println(sort.take(2)) return Entry(mx.max(e.mx), sort[0], if (sort.size >= 2) sort[1] else null) } fun merge0(e: Entry): Entry { var mn2 = this.mn1.max(e.mn1) if (this.mn2 != null) mn2 = mn2.min(this.mn2) if (e.mn2 != null) mn2 = mn2.min(e.mn2) return Entry(mx.max(e.mx), this.mn1.min(e.mn1), mn2) } } class Solver(stream: InputStream, private val out: java.io.PrintWriter) { private val reader = BufferedReader(InputStreamReader(stream), 32768) private val N = ni() private val A = na(N) fun solve() { val tbl = mutableListOf(Array(N){Entry(Val(it, A[it]), Val(it, A[it]), null)}) var k = 1 while (2 * k <= N) { val lst = tbl.last() val build = Array(N){lst[it]} for (i in 0 until N) { if (i + k < N) { build[i] = lst[i].merge0(lst[i + k]) } else { build[i] = lst[i] } } tbl += build k *= 2 } val n2k = IntArray(N + 1) val n2ksize = IntArray(N + 1) k = 1 var ki = 0 for (n in 1..N) { if (k * 2 == n) { k *= 2 ki++ } n2k[n] = ki n2ksize[n] = k } debug(n2k) debug(n2ksize) debug{"${tbl[1][2]}"} var ans = 0L for (i in 0 until N) { val len = findMax(1, N - i) { len -> val k = n2k[len] val ksize = n2ksize[len] var e = tbl[k][i] val j = len - ksize e = e.merge(tbl[k][i + j]) e.mn2 != null && e.mn1.a + e.mn2!!.a >= e.mx.a } debug{"$i $len"} if (len > 1) ans += len - 1 } out.println(ans) } private val isDebug = try { // なんか本番でエラーでる System.getenv("MY_DEBUG") != null } catch (t: Throwable) { false } private var tokenizer: StringTokenizer? = null private fun next(): String { while (tokenizer == null || !tokenizer!!.hasMoreTokens()) { tokenizer = StringTokenizer(reader.readLine()) } return tokenizer!!.nextToken() } private fun ni() = next().toInt() private fun nl() = next().toLong() private fun ns() = next() private fun na(n: Int, offset: Int = 0): IntArray { return IntArray(n) { ni() + offset } } private fun nal(n: Int, offset: Int = 0): LongArray { val res = LongArray(n) for (i in 0 until n) { res[i] = nl() + offset } return res } private fun na2(n: Int, offset: Int = 0): Array { val a = Array(2){IntArray(n)} for (i in 0 until n) { for (e in a) { e[i] = ni() + offset } } return a } private inline fun debug(msg: () -> String) { if (isDebug) System.err.println(msg()) } /** * コーナーケースでエラー出たりするので、debug(dp[1])のように添え字付きの場合はdebug{}をつかうこと */ private inline fun debug(a: LongArray) { debug { a.joinToString(" ") } } private inline fun debug(a: IntArray) { debug { a.joinToString(" ") } } private inline fun debug(a: BooleanArray) { debug { toString(a) } } private inline fun toString(a: BooleanArray) = run{a.map { if (it) 1 else 0 }.joinToString("")} private inline fun debugDim(A: Array) { if (isDebug) { for (a in A) { debug(a) } } } private inline fun debugDim(A: Array) { if (isDebug) { for (a in A) { debug(a) } } } private inline fun debugDim(A: Array) { if (isDebug) { for (a in A) { debug(a) } } } /** * 勝手にimport消されるのを防ぎたい */ private fun hoge() { min(1, 2) max(1, 2) abs(-10) } private inline fun assert(b: Boolean) = run{if (!b) throw AssertionError()} } fun main() { val out = java.io.PrintWriter(System.out) Solver(System.`in`, out).solve() out.flush() }