Problem:
Score : 600 points

Problem Statement

We have N colored balls arranged in a row from left to right; the color of the i-th ball from the left is c_i.

You are given Q queries. The i-th query is as follows: how many different colors do the l_i-th through r_i-th balls from the left have?

Constraints

1\leq N,Q \leq 5 \times 10^5

1\leq c_i \leq N

1\leq l_i \leq r_i \leq N

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N Q
c_1 c_2 \cdots c_N
l_1 r_1
l_2 r_2
:
l_Q r_Q

Output

Print Q lines. The i-th line should contain the response to the i-th query.

Sample Input 1

4 3
1 2 1 3
1 3
2 4
3 3

Sample Output 1

2
3
1

The 1-st, 2-nd, and 3-rd balls from the left have the colors 1, 2, and 1 - two different colors.

The 2-st, 3-rd, and 4-th balls from the left have the colors 2, 1, and 3 - three different colors.

The 3-rd ball from the left has the color 1 - just one color.

Sample Input 2

10 10
2 5 6 5 2 1 7 9 7 2
5 5
2 4
6 7
2 2
7 8
7 9
1 8
6 9
8 10
6 8

Sample Output 2

1
2
2
1
2
2
6
3
3
3

Solution in Go (1.14.1) (judge verdict: Time Limit Exceeded)

package main

import (
  "bufio"
  "os"
  "strconv"
  "strings"
  "fmt"
)

type Evaluator func(a, b interface{}) interface{}
func Eval(a, b interface{}) interface{} {
  x := a.(map[int]interface{})
  y := b.(map[int]interface{})
  z := make(map[int]interface{})
  for k := range x { z[k] = 1 }
  for k := range y { z[k] = 1 }
  return z
} 
type SegmentTree struct {
  size  int
  data  []interface{}
  inf   interface{}
  eval  Evaluator
}
func InitSegmentTree(N int, inf interface{}, eval Evaluator) *SegmentTree {
  size := 1
  for size < N {
    size *= 2
  }
  S := make([]interface{}, size * 2)
  for i := range S {
    S[i] = inf
  }
  return &SegmentTree{
    size: size,
    data: S,
    inf:  inf,
    eval: eval,
  }
}
func (ST *SegmentTree) Update(index int, value interface{}) {
  idx := ST.size + index
  ST.data[idx] = value
  for idx > 1 {
    parent := idx / 2
    ST.data[parent] = ST.eval(ST.data[2 * parent], ST.data[2 * parent + 1])
    idx = parent
  }
}
func (ST *SegmentTree) Get(from, to, index, left, right int) interface{} {
  // get [from, to)
  if to <= left || right <= from { return ST.inf }
  if from <= left && right <= to { return ST.data[index] }
  m := (left + right) / 2
  lval := ST.Get(from, to, 2 * index, left, m)
  rval := ST.Get(from, to, 2 * index + 1, m, right)
  return ST.eval(lval, rval)
}
func (ST *SegmentTree) Query(from, to int) interface{} {
  return ST.Get(from, to, 1, 0, ST.size)
}

func Solve() {
  var N, Q, L, R int
  NextInt(&N, &Q)
  var C []int
  NextIntSlice(&C)
  Z := make(map[int]interface{})
  ST := InitSegmentTree(N, Z, Eval)
  for i, c := range C {
    p := make(map[int]interface{})
    p[c] = 1
    ST.Update(i, p)
  }
  for q := 0; q < Q; q++ {
    NextInt(&L, &R)
    P := ST.Query(L - 1, R).(map[int]interface{})
    Write(len(P))
  }
}

func main() {
  Solve()
  Output()
}

var reader = bufio.NewReaderSize(os.Stdin, 1000000)
var writer = bufio.NewWriter(os.Stdout)
func NextLine() string {
  buffer := make([]byte, 0)
  for true {
    line, isPrefix, err := reader.ReadLine()
    if err != nil { panic(err) }
    buffer = append(buffer, line...)
    if !isPrefix { break }
  }
  return string(buffer)
}
func NextInt(A ...*int) {
  L := strings.Split(NextLine(), " ")
  for i, a := range A {
    *a, _ = strconv.Atoi(L[i])
  }
}
func NextIntSlice(A *[]int) {
  L := strings.Split(NextLine(), " ")
  if len(L) == 1 && L[0] == "" {
    (*A) = make([]int, 0)
    return
  }
  (*A) = make([]int, len(L))
  for i, l := range L {
    (*A)[i], _ = strconv.Atoi(l)
  }
}
func NextFloat(A ...*float64) {
  L := strings.Split(NextLine(), " ")
  for i, a := range A {
    *a, _ = strconv.ParseFloat(L[i], 64)
  }
}
func NextFloatSlice(A *[]float64) {
  L := strings.Split(NextLine(), " ")
  if len(L) == 1 && L[0] == "" {
    (*A) = make([]float64, 0)
    return
  }
  (*A) = make([]float64, len(L))
  for i, l := range L {
    (*A)[i], _ = strconv.ParseFloat(l, 64)
  }
}
func Write(S ...interface{}) {
  fmt.Fprintln(writer, S...)
}
func WriteIntSlice(A []int) {
  B := make([]interface{}, len(A))
  for i, a := range A { B[i] = a }
  fmt.Fprintln(writer, B...)
}
func Output() {
  _ = writer.Flush()
}
func MaxInt(A ...int) int {
  max := A[0]
  for _, a := range A {
    if max < a { max = a }
  }
  return max
}
func MinInt(A ...int) int {
  min := A[0]
  for _, a := range A {
    if a < min { min = a }
  }
  return min
}
func SumInt(A ...int) int {
  sum := 0
  for _, a := range A {
    sum += a
  }
  return sum
}
func AbsInt(x int) int {
  if x < 0 { x = -x }
  return x
}
func Ceil(x, y int) int {
  a := x / y
  if x % y > 0 { a++ }
  return a
}