Problem p03987 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
#pragma GCC optimize("O2")
#pragma GCC optimize("unroll-loops")
// #pragma GCC optimize("no-stack-protector,fast-math")

using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<pii, int> piii;
typedef pair<ll, ll> pll;
#define debug(x) cerr << #x << '=' << (x) << endl;
#define debugp(x)                                                              \
  cerr << #x << "= {" << (x.first) << ", " << (x.second) << "}" << endl;
#define debug2(x, y)                                                           \
  cerr << "{" << #x << ", " << #y << "} = {" << (x) << ", " << (y) << "}"      \
       << endl;
#define debugv(v)                                                              \
  cerr << #v << " : ";                                                         \
  for (auto x : v)                                                             \
    cerr << x << ' ';                                                          \
  cerr << endl;
#define all(x) x.begin(), x.end()
#define pb push_back
#define kill(x) return cout << x << '\n', 0;

const ld eps = 1e-7;
const int inf = 1000000010;
const ll INF = 10000000000000010LL;
const int mod = 1000000007;
const int MAXN = 100010, LOG = 20;

ll n, m, k, u, v, x, y, t, a, b, ans;
int A[MAXN];
ll L[MAXN], R[MAXN];

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  // freopen("input.txt", "r", stdin);
  // freopen("output.txt", "w", stdout);
  cin >> n;
  for (int i = 1; i <= n; i++)
    cin >> A[i];
  for (int i = 1; i <= n; i++)
    for (L[i] = i - 1; L[i] && A[L[i]] >= A[i]; L[i] = L[L[i]])
      ;
  for (int i = n; i; i--)
    for (R[i] = i + 1; R[i] <= n && A[R[i]] > A[i]; R[i] = R[R[i]])
      ;
  for (int i = 1; i <= n; i++)
    ans += A[i] * (i - L[i]) * (R[i] - i);
  cout << ans << '\n';

  return 0;
}
/*
3 2
1 2
2 3

*/

Fixed submission:
#include <bits/stdc++.h>
#pragma GCC optimize("O2")
#pragma GCC optimize("unroll-loops")
// #pragma GCC optimize("no-stack-protector,fast-math")

using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<pii, int> piii;
typedef pair<ll, ll> pll;
#define debug(x) cerr << #x << '=' << (x) << endl;
#define debugp(x)                                                              \
  cerr << #x << "= {" << (x.first) << ", " << (x.second) << "}" << endl;
#define debug2(x, y)                                                           \
  cerr << "{" << #x << ", " << #y << "} = {" << (x) << ", " << (y) << "}"      \
       << endl;
#define debugv(v)                                                              \
  cerr << #v << " : ";                                                         \
  for (auto x : v)                                                             \
    cerr << x << ' ';                                                          \
  cerr << endl;
#define all(x) x.begin(), x.end()
#define pb push_back
#define kill(x) return cout << x << '\n', 0;

const ld eps = 1e-7;
const int inf = 1000000010;
const ll INF = 10000000000000010LL;
const int mod = 1000000007;
const int MAXN = 200010, LOG = 20;

ll n, m, k, u, v, x, y, t, a, b, ans;
int A[MAXN];
ll L[MAXN], R[MAXN];

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  // freopen("input.txt", "r", stdin);
  // freopen("output.txt", "w", stdout);
  cin >> n;
  for (int i = 1; i <= n; i++)
    cin >> A[i];
  for (int i = 1; i <= n; i++)
    for (L[i] = i - 1; L[i] && A[L[i]] >= A[i]; L[i] = L[L[i]])
      ;
  for (int i = n; i; i--)
    for (R[i] = i + 1; R[i] <= n && A[R[i]] > A[i]; R[i] = R[R[i]])
      ;
  for (int i = 1; i <= n; i++)
    ans += A[i] * (i - L[i]) * (R[i] - i);
  cout << ans << '\n';

  return 0;
}
/*
3 2
1 2
2 3

*/