Problem p02791 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <bits/stdc++.h>
#include <cmath>
#include <cstdio>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <utility>
#include <vector>

#define fir first
#define sec second
#define sz(s) (s).size()
#define pb push_back
#define get(n) scanf("%d", &n);
#define gets(s)                                                                \
  string s;                                                                    \
  cin >> (s);
#define prfi(n) printf("%d", &n);
#define prfd(n) printf("%lf", &n);
#define All(s) (s).begin(), (s).end()
#define rep(i, j) for (int(i) = 0; (i) < (j); (i)++)
#define For(i, j, k) for (int(i) = (j); (i) < (k); (i)++)
#define drep(i, j) for (int(i) = (j); (i) >= 0; (i)--)
#define Ford(i, j, k) for (int(i) = (j); i >= (k); i--)
#define vfor(c, v) for (auto(c) : (v))
#define lpi(n) for (int i = 0; i < (n); i++)
#define lpj(n) for (int j = 0; j < (n); j++)
#define lpz(n) for (int z = 0; z < (n); z++)
#define mem(a, b) memset(a, b, sizeof(a));
#define dump(x) std::cout << #x << " = " << (x) << std::endl;
#define debug(x)                                                               \
  cout << #x << " = " << (x) << " (L" << __LINE__ << ")"                       \
       << " " << __FILE__ << endl;
using ll = long long;
using ld = long double;
using pii = std::pair<int, int>;
using pll = std::pair<ll, ll>;
using vi = std::vector<int>;
using vvi = std::vector<vi>;
using vll = std::vector<ll>;
using vvll = std::vector<vll>;
using vd = std::vector<double>;
using vvd = std::vector<vd>;
using qi = std::queue<int>;
using vpii = std::vector<std::pair<int, int>>;
using vpll = std::vector<pll>;
using namespace std;

const int Mod = (1e9) + 7;
const int INF = 1e9 + 19;
const ll INFL = 1e18 + 19;
const int dx[] = {-1, 0, 0, 1};
const int dy[] = {0, -1, 1, 0};
const int dx2[] = {-1, -1, -1, 0, 0, 0, 1, 1, 1};
const int dy2[] = {1, 0, -1, 1, 0, -1, 1, 0, -1};
//_____________________________________Templates_________________________________________//

template <class T1, class T2> inline void chmin(T1 &a, T2 b) {
  if (a > b)
    a = b;
}
template <class T1, class T2> inline void chmax(T1 &a, T2 b) {
  if (a < b)
    a = b;
}
template <class T> inline void swap(T &a, T &b) {
  T c = a;
  a = b;
  b = c;
}
template <class T> inline void pri(T a) { cout << a << endl; }
template <class Z> using vec = vector<Z>;
// mainly use for dynamic prog
template <class T1, class T2> void update(T1 &a, T2 b) {
  a += b;
  if (a > Mod)
    a %= Mod;
}

inline void IN(void) { return; }

template <typename First, typename... Rest>
void IN(First &first, Rest &...rest) {
  cin >> first;
  IN(rest...);
  return;
}

inline void OUT(void) {
  cout << "\n";
  return;
}

template <typename First, typename... Rest>
void OUT(First first, Rest... rest) {
  cout << first << " ";
  OUT(rest...);
  return;
}

bool pairsort(pll pl, pll pr) {
  if (pl.first == pr.first)
    return pl.second > pr.second;
  return pl.first < pr.first;
}

int cntbit(ll a, int n, int j) {
  int res = 0;
  For(i, j, n) {
    if (a >> i & 1) {
      res++;
    }
  }
  return res;
}
vector<int> make_bit(int a) {
  vector<int> res;
  lpi(32) if (a & (1 << i)) res.pb(i);
  return res;
}
bool stdbit(int a, int b) { return a & (1 << b); }
int GCD(int a, int b) {
  if (b > a)
    return GCD(b, a);
  if (a % b == 0)
    return b;
  else
    return GCD(b, a % b);
}
int LCM(int a, int b) { return a * b / GCD(a, b); }
int roundup(int a, int b) {
  if (a % b == 0)
    return a / b;
  else
    return (a + b) / b;
}
int rounddown(int a, int b) {
  if (a % b == 0)
    return a / b;
  else {
    return (a - b) / b;
  }
}
ll GetDiviserCount(ll N) // 約数の個数
{
  ll res = 1;
  For(i, 2, sqrt(N) + 1) {
    ll cnt = 0;
    while (N % i == 0) {
      cnt++;
      N /= i;
    }
    res *= (cnt + 1);
    if (N == 1)
      break;
  }
  if (N != 1)
    res *= 2;
  return res;
}
vll GetDivisor(ll N) // 約数列挙
{
  vll res;
  for (ll i = 1; i * i <= N; i++) {
    if (N % i == 0) {
      res.pb(i);
      if (i * i != N)
        res.pb(N / i);
    }
  }
  sort(All(res));
  return res;
}
//_____________________　following sorce code_________________________//
const int max_n = 3 * (1e5) + 1;
const int max_m = 83 * (1e5) + 1;
struct BIT {
  using T = ll;
  vector<T> data;
  T UNIT;
  int n;

  BIT(int n, T a) : n(n), UNIT(a) { data.resize(n + 1, UNIT); }

  T sum(int i) {
    int s = 0;
    while (i > 0) {
      s += data[i];
      i -= i & -i;
    }
    return s;
  }

  void add(int i, T x) {
    while (i <= n) {
      data[i] += x;
      i += i & -i;
    }
  }
  T range(int r, int l) { return sum(r) - sum(l - 1); }

  int lower_bound(T w) {
    if (w <= 0)
      return 0;
    int x = 0;
    int pos = 1, N = n + 1;
    while (pos * 2 <= N) {
      pos *= 2;
    }
    for (int k = pos; k > 0; k /= 2) {
      if (x + k <= N && data[x + k] <= w) {
        w -= data[x + k];
        x += k;
      }
    }
    return x + 1;
  }
};
int n, m, k, q;
ll N;
int h, w;
vvi tree;
string S;
int a, b, c;
vi v;
int ans;
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  IN(n);
  vi p(n);
  lpi(n) IN(p[i]);
  BIT bt(20020, 0);
  ans = 0;
  rep(i, n) {
    int sum = bt.sum(p[i]);
    if (sum == 0)
      ans++;
    bt.add(p[i], 1);
  }
  cout << ans << endl;
  // for(auto c : ans){cout << c << endl;}
  // cout << fixed << setprecision(15) << ans << endl;
  return 0;
}

Fixed submission:
#include <algorithm>
#include <bits/stdc++.h>
#include <cmath>
#include <cstdio>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <utility>
#include <vector>

#define fir first
#define sec second
#define sz(s) (s).size()
#define pb push_back
#define get(n) scanf("%d", &n);
#define gets(s)                                                                \
  string s;                                                                    \
  cin >> (s);
#define prfi(n) printf("%d", &n);
#define prfd(n) printf("%lf", &n);
#define All(s) (s).begin(), (s).end()
#define rep(i, j) for (int(i) = 0; (i) < (j); (i)++)
#define For(i, j, k) for (int(i) = (j); (i) < (k); (i)++)
#define drep(i, j) for (int(i) = (j); (i) >= 0; (i)--)
#define Ford(i, j, k) for (int(i) = (j); i >= (k); i--)
#define vfor(c, v) for (auto(c) : (v))
#define lpi(n) for (int i = 0; i < (n); i++)
#define lpj(n) for (int j = 0; j < (n); j++)
#define lpz(n) for (int z = 0; z < (n); z++)
#define mem(a, b) memset(a, b, sizeof(a));
#define dump(x) std::cout << #x << " = " << (x) << std::endl;
#define debug(x)                                                               \
  cout << #x << " = " << (x) << " (L" << __LINE__ << ")"                       \
       << " " << __FILE__ << endl;
using ll = long long;
using ld = long double;
using pii = std::pair<int, int>;
using pll = std::pair<ll, ll>;
using vi = std::vector<int>;
using vvi = std::vector<vi>;
using vll = std::vector<ll>;
using vvll = std::vector<vll>;
using vd = std::vector<double>;
using vvd = std::vector<vd>;
using qi = std::queue<int>;
using vpii = std::vector<std::pair<int, int>>;
using vpll = std::vector<pll>;
using namespace std;

const int Mod = (1e9) + 7;
const int INF = 1e9 + 19;
const ll INFL = 1e18 + 19;
const int dx[] = {-1, 0, 0, 1};
const int dy[] = {0, -1, 1, 0};
const int dx2[] = {-1, -1, -1, 0, 0, 0, 1, 1, 1};
const int dy2[] = {1, 0, -1, 1, 0, -1, 1, 0, -1};
//_____________________________________Templates_________________________________________//

template <class T1, class T2> inline void chmin(T1 &a, T2 b) {
  if (a > b)
    a = b;
}
template <class T1, class T2> inline void chmax(T1 &a, T2 b) {
  if (a < b)
    a = b;
}
template <class T> inline void swap(T &a, T &b) {
  T c = a;
  a = b;
  b = c;
}
template <class T> inline void pri(T a) { cout << a << endl; }
template <class Z> using vec = vector<Z>;
// mainly use for dynamic prog
template <class T1, class T2> void update(T1 &a, T2 b) {
  a += b;
  if (a > Mod)
    a %= Mod;
}

inline void IN(void) { return; }

template <typename First, typename... Rest>
void IN(First &first, Rest &...rest) {
  cin >> first;
  IN(rest...);
  return;
}

inline void OUT(void) {
  cout << "\n";
  return;
}

template <typename First, typename... Rest>
void OUT(First first, Rest... rest) {
  cout << first << " ";
  OUT(rest...);
  return;
}

bool pairsort(pll pl, pll pr) {
  if (pl.first == pr.first)
    return pl.second > pr.second;
  return pl.first < pr.first;
}

int cntbit(ll a, int n, int j) {
  int res = 0;
  For(i, j, n) {
    if (a >> i & 1) {
      res++;
    }
  }
  return res;
}
vector<int> make_bit(int a) {
  vector<int> res;
  lpi(32) if (a & (1 << i)) res.pb(i);
  return res;
}
bool stdbit(int a, int b) { return a & (1 << b); }
int GCD(int a, int b) {
  if (b > a)
    return GCD(b, a);
  if (a % b == 0)
    return b;
  else
    return GCD(b, a % b);
}
int LCM(int a, int b) { return a * b / GCD(a, b); }
int roundup(int a, int b) {
  if (a % b == 0)
    return a / b;
  else
    return (a + b) / b;
}
int rounddown(int a, int b) {
  if (a % b == 0)
    return a / b;
  else {
    return (a - b) / b;
  }
}
ll GetDiviserCount(ll N) // 約数の個数
{
  ll res = 1;
  For(i, 2, sqrt(N) + 1) {
    ll cnt = 0;
    while (N % i == 0) {
      cnt++;
      N /= i;
    }
    res *= (cnt + 1);
    if (N == 1)
      break;
  }
  if (N != 1)
    res *= 2;
  return res;
}
vll GetDivisor(ll N) // 約数列挙
{
  vll res;
  for (ll i = 1; i * i <= N; i++) {
    if (N % i == 0) {
      res.pb(i);
      if (i * i != N)
        res.pb(N / i);
    }
  }
  sort(All(res));
  return res;
}
//_____________________　following sorce code_________________________//
const int max_n = 3 * (1e5) + 1;
const int max_m = 83 * (1e5) + 1;
struct BIT {
  using T = ll;
  vector<T> data;
  T UNIT;
  int n;

  BIT(int n, T a) : n(n), UNIT(a) { data.resize(n + 1, UNIT); }

  T sum(int i) {
    int s = 0;
    while (i > 0) {
      s += data[i];
      i -= i & -i;
    }
    return s;
  }

  void add(int i, T x) {
    while (i <= n) {
      data[i] += x;
      i += i & -i;
    }
  }
  T range(int r, int l) { return sum(r) - sum(l - 1); }

  int lower_bound(T w) {
    if (w <= 0)
      return 0;
    int x = 0;
    int pos = 1, N = n + 1;
    while (pos * 2 <= N) {
      pos *= 2;
    }
    for (int k = pos; k > 0; k /= 2) {
      if (x + k <= N && data[x + k] <= w) {
        w -= data[x + k];
        x += k;
      }
    }
    return x + 1;
  }
};
int n, m, k, q;
ll N;
int h, w;
vvi tree;
string S;
int a, b, c;
vi v;
int ans;
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  IN(n);
  vi p(n);
  lpi(n) IN(p[i]);
  BIT bt(200200, 0);
  ans = 0;
  rep(i, n) {
    int sum = bt.sum(p[i]);
    if (sum == 0)
      ans++;
    bt.add(p[i], 1);
  }
  cout << ans << endl;
  // for(auto c : ans){cout << c << endl;}
  // cout << fixed << setprecision(15) << ans << endl;
  return 0;
}