Problem p02599 (C++)

Buggy submission (status: Runtime Error):
// #define _GLIBCXX_DEBUG

#include <bits/stdc++.h>
using namespace std;

#define endl '\n'
#define lfs cout << fixed << setprecision(10)
#define ALL(a) (a).begin(), (a).end()
#define ALLR(a) (a).rbegin(), (a).rend()
#define spa << " " <<
#define fi first
#define se second
#define MP make_pair
#define MT make_tuple
#define PB push_back
#define EB emplace_back
#define rep(i, n, m) for (ll i = (n); i < (ll)(m); i++)
#define rrep(i, n, m) for (ll i = (ll)(m)-1; i >= (ll)(n); i--)
using ll = long long;
using ld = long double;
const ll MOD1 = 1e9 + 7;
const ll MOD9 = 998244353;
const ll INF = 1e18;
using P = pair<ll, ll>;
template <typename T1, typename T2> bool chmin(T1 &a, T2 b) {
  if (a > b) {
    a = b;
    return true;
  } else
    return false;
}
template <typename T1, typename T2> bool chmax(T1 &a, T2 b) {
  if (a < b) {
    a = b;
    return true;
  } else
    return false;
}
ll median(ll a, ll b, ll c) {
  return a + b + c - max({a, b, c}) - min({a, b, c});
}
void ans1(bool x) {
  if (x)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
}
void ans2(bool x) {
  if (x)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
}
void ans3(bool x) {
  if (x)
    cout << "Yay!" << endl;
  else
    cout << ":(" << endl;
}
template <typename T1, typename T2> void ans(bool x, T1 y, T2 z) {
  if (x)
    cout << y << endl;
  else
    cout << z << endl;
}
template <typename T> void debug(vector<vector<T>> &v, ll h, ll w) {
  for (ll i = 0; i < h; i++) {
    cout << v[i][0];
    for (ll j = 1; j < w; j++)
      cout spa v[i][j];
    cout << endl;
  }
};
void debug(vector<string> &v, ll h, ll w) {
  for (ll i = 0; i < h; i++) {
    for (ll j = 0; j < w; j++)
      cout << v[i][j];
    cout << endl;
  }
};
template <typename T> void debug(vector<T> &v, ll n) {
  if (n != 0)
    cout << v[0];
  for (ll i = 1; i < n; i++)
    cout spa v[i];
  cout << endl;
};
template <typename T> vector<vector<T>> vec(ll x, ll y, T w) {
  vector<vector<T>> v(x, vector<T>(y, w));
  return v;
}
ll gcd(ll x, ll y) {
  ll r;
  while (y != 0 && (r = x % y) != 0) {
    x = y;
    y = r;
  }
  return y == 0 ? x : y;
}
vector<ll> dx = {1, -1, 0, 0, 1, 1, -1, -1};
vector<ll> dy = {0, 0, 1, -1, 1, -1, 1, -1};
template <typename T> vector<T> make_v(size_t a, T b) {
  return vector<T>(a, b);
}
template <typename... Ts> auto make_v(size_t a, Ts... ts) {
  return vector<decltype(make_v(ts...))>(a, make_v(ts...));
}
template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  return os << p.first << " " << p.second;
}
// mt19937 mt(chrono::steady_clock::now().time_since_epoch().count());
template <typename T> struct BIT {
  ll n;
  ll k = 1;
  vector<T> data;
  BIT() = default;
  BIT(ll size) : n(size) {
    data.assign(n, 0);
    while (k * 2 <= n)
      k *= 2;
  }
  void add(ll a, T w) {
    for (ll i = a + 1; i <= n; i += i & -i)
      data[i - 1] += w;
  }
  T sum(ll a) {
    if (a < 0)
      return 0;
    T ret = 0;
    for (ll i = a + 1; i > 0; i -= i & -i)
      ret += data[i - 1];
    return ret;
  }
  T sum(ll a, ll b) { return a > b ? 0 : sum(b) - sum(a - 1); }
  T operator[](ll pos) { return sum(pos, pos); }
  ll lower_bound(ll x) {
    ll ret = 0;
    for (ll i = k; i > 0; i /= 2) {
      if (ret + i <= n && data[ret + i - 1] < x) {
        x -= data[ret + i - 1];
        ret += i;
      }
    }
    return ret;
  }
  void print() {
    for (ll i = 0; i < n; i++) {
      if (i != 0)
        cout << " ";
      cout << (*this)[i];
    }
    cout << endl;
  }
};
int main() {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  ll res = 0, buf = 0;
  bool judge = true;
  ll n, q;
  cin >> n >> q;
  vector<ll> c(n), l(q), r(q);
  rep(i, 0, n) cin >> c[i], c[i]--;
  ;
  vector<vector<ll>> g(n);
  rep(i, 0, q) {
    cin >> l[i] >> r[i];
    l[i]--;
    r[i]--;
    g[r[i]].PB(i);
  }
  BIT<ll> bit(n);
  vector<ll> ret(q);
  vector<ll> pre(100005, -1);
  rep(i, 0, n) {
    bit.add(i, 1);
    if (pre[c[i]] != -1)
      bit.add(pre[c[i]], -1);
    pre[c[i]] = i;
    for (auto z : g[i])
      ret[z] = bit.sum(l[z], r[z]);
  }
  rep(i, 0, q) cout << ret[i] << endl;
  return 0;
}

Fixed submission:
// #define _GLIBCXX_DEBUG

#include <bits/stdc++.h>
using namespace std;

#define endl '\n'
#define lfs cout << fixed << setprecision(10)
#define ALL(a) (a).begin(), (a).end()
#define ALLR(a) (a).rbegin(), (a).rend()
#define spa << " " <<
#define fi first
#define se second
#define MP make_pair
#define MT make_tuple
#define PB push_back
#define EB emplace_back
#define rep(i, n, m) for (ll i = (n); i < (ll)(m); i++)
#define rrep(i, n, m) for (ll i = (ll)(m)-1; i >= (ll)(n); i--)
using ll = long long;
using ld = long double;
const ll MOD1 = 1e9 + 7;
const ll MOD9 = 998244353;
const ll INF = 1e18;
using P = pair<ll, ll>;
template <typename T1, typename T2> bool chmin(T1 &a, T2 b) {
  if (a > b) {
    a = b;
    return true;
  } else
    return false;
}
template <typename T1, typename T2> bool chmax(T1 &a, T2 b) {
  if (a < b) {
    a = b;
    return true;
  } else
    return false;
}
ll median(ll a, ll b, ll c) {
  return a + b + c - max({a, b, c}) - min({a, b, c});
}
void ans1(bool x) {
  if (x)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
}
void ans2(bool x) {
  if (x)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
}
void ans3(bool x) {
  if (x)
    cout << "Yay!" << endl;
  else
    cout << ":(" << endl;
}
template <typename T1, typename T2> void ans(bool x, T1 y, T2 z) {
  if (x)
    cout << y << endl;
  else
    cout << z << endl;
}
template <typename T> void debug(vector<vector<T>> &v, ll h, ll w) {
  for (ll i = 0; i < h; i++) {
    cout << v[i][0];
    for (ll j = 1; j < w; j++)
      cout spa v[i][j];
    cout << endl;
  }
};
void debug(vector<string> &v, ll h, ll w) {
  for (ll i = 0; i < h; i++) {
    for (ll j = 0; j < w; j++)
      cout << v[i][j];
    cout << endl;
  }
};
template <typename T> void debug(vector<T> &v, ll n) {
  if (n != 0)
    cout << v[0];
  for (ll i = 1; i < n; i++)
    cout spa v[i];
  cout << endl;
};
template <typename T> vector<vector<T>> vec(ll x, ll y, T w) {
  vector<vector<T>> v(x, vector<T>(y, w));
  return v;
}
ll gcd(ll x, ll y) {
  ll r;
  while (y != 0 && (r = x % y) != 0) {
    x = y;
    y = r;
  }
  return y == 0 ? x : y;
}
vector<ll> dx = {1, -1, 0, 0, 1, 1, -1, -1};
vector<ll> dy = {0, 0, 1, -1, 1, -1, 1, -1};
template <typename T> vector<T> make_v(size_t a, T b) {
  return vector<T>(a, b);
}
template <typename... Ts> auto make_v(size_t a, Ts... ts) {
  return vector<decltype(make_v(ts...))>(a, make_v(ts...));
}
template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  return os << p.first << " " << p.second;
}
// mt19937 mt(chrono::steady_clock::now().time_since_epoch().count());
template <typename T> struct BIT {
  ll n;
  ll k = 1;
  vector<T> data;
  BIT() = default;
  BIT(ll size) : n(size) {
    data.assign(n, 0);
    while (k * 2 <= n)
      k *= 2;
  }
  void add(ll a, T w) {
    for (ll i = a + 1; i <= n; i += i & -i)
      data[i - 1] += w;
  }
  T sum(ll a) {
    if (a < 0)
      return 0;
    T ret = 0;
    for (ll i = a + 1; i > 0; i -= i & -i)
      ret += data[i - 1];
    return ret;
  }
  T sum(ll a, ll b) { return a > b ? 0 : sum(b) - sum(a - 1); }
  T operator[](ll pos) { return sum(pos, pos); }
  ll lower_bound(ll x) {
    ll ret = 0;
    for (ll i = k; i > 0; i /= 2) {
      if (ret + i <= n && data[ret + i - 1] < x) {
        x -= data[ret + i - 1];
        ret += i;
      }
    }
    return ret;
  }
  void print() {
    for (ll i = 0; i < n; i++) {
      if (i != 0)
        cout << " ";
      cout << (*this)[i];
    }
    cout << endl;
  }
};
int main() {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  ll res = 0, buf = 0;
  bool judge = true;
  ll n, q;
  cin >> n >> q;
  vector<ll> c(n), l(q), r(q);
  rep(i, 0, n) cin >> c[i], c[i]--;
  ;
  vector<vector<ll>> g(n);
  rep(i, 0, q) {
    cin >> l[i] >> r[i];
    l[i]--;
    r[i]--;
    g[r[i]].PB(i);
  }
  BIT<ll> bit(n);
  vector<ll> ret(q);
  vector<ll> pre(500005, -1);
  rep(i, 0, n) {
    bit.add(i, 1);
    if (pre[c[i]] != -1)
      bit.add(pre[c[i]], -1);
    pre[c[i]] = i;
    for (auto z : g[i])
      ret[z] = bit.sum(l[z], r[z]);
  }
  rep(i, 0, q) cout << ret[i] << endl;
  return 0;
}