Language: C++

#pragma target("avx")
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> P;
typedef vector<ll> V;
typedef unordered_map<ll, ll> U_MAP;
typedef priority_queue<ll> pq;
typedef priority_queue<ll, vector<ll>, greater<ll>> rpq;
constxpr int INF = 1e9, MOD = 1e9 + 7, ohara = 1e6 + 10;
const ll LINF = 1e18;

#define rep(i, n) for (ll(i) = 0; (i) < (int)(n); (i)++)
#define rrep(i, a, b) for (ll i = (a); i < (b); i++)
#define rrrep(i, a, b) for (ll i = (a); i >= (b); i--)
#define all(v) (v).begin(), (v).end()
#define Size(n) (n).size()
#define Cout(x) cout << (x) << endl
#define doublecout(a) cout << fixed << setprecision(15) << a << endl;
#define fi first
#define se second
#define m_p make_pair
#define p_b push_back
string to_string(string s) { return '"' + s + '"'; }
string to_string(const char* s) { return to_string((string)s); }
string to_string(bool b) { return (b ? "true" : "false"); }
template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}
template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto& x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)

//------ Believe yourself as a genius!!!!!! ------

int dy[] = {1, 0, -1, 0};
int dx[] = {0, 1, 0, -1};
// int dy[]={-1,0,1,-1,1,-1,0,1};int dx[]={-1,-1,-1,0,0,1,1,1};
string alph("abcdefghijklmnopqrstuvwxyz"), s;
ll n, cnt, ans, a, b, c, d, tmp, m, h, w, x, y, sum, k, q;
ll f[ohara], fr[ohara];

ll mod_pow(ll xx, ll nn, ll mod) {
  ll ret = 1;
  while (nn > 0) {
    if (nn & 1) ret = ret * xx % mod;
    xx = xx * xx % mod;
    nn >>= 1;
  }
  return ret;
}

ll ncr(ll nn, ll r) {
  if (nn < r) return 0;
  return f[nn] * fr[r] % MOD * fr[nn - r] % MOD;
}

int main(void) {
  cin.tie(0);
  cout.tie(0);
  ios::sync_with_stdio(false);

  cin >> n >> k;
  f[0] = 1;
  rrep(i, 1, n + 3) { f[i] = f[i - 1] * i % MOD; }
  fr[n + 2] = mod_pow(f[n + 2], MOD - 2, MOD);
  rrrep(i, n + 1, 0) { fr[i] = fr[i + 1] * (i + 1) % MOD; }
  ans = 1;
  rrep(i, 1, min(n, k + 1)) {
    ans += ncr(n, i) * ncr(n - 1, i);
    ans %= MOD;
  }
  Cout(ans);
  return 0;
}


Compiler output:
a.cc:13:1: error: 'constxpr' does not name a type; did you mean 'constexpr'?
   13 | constxpr int INF = 1e9, MOD = 1e9 + 7, ohara = 1e6 + 10;
      | ^~~~~~~~
      | constexpr
a.cc:63:6: error: 'ohara' was not declared in this scope
   63 | ll f[ohara], fr[ohara];
      |      ^~~~~
a.cc:63:17: error: 'ohara' was not declared in this scope
   63 | ll f[ohara], fr[ohara];
      |                 ^~~~~
a.cc: In function 'll ncr(ll, ll)':
a.cc:77:10: error: 'f' was not declared in this scope
   77 |   return f[nn] * fr[r] % MOD * fr[nn - r] % MOD;
      |          ^
a.cc:77:18: error: 'fr' was not declared in this scope; did you mean 'r'?
   77 |   return f[nn] * fr[r] % MOD * fr[nn - r] % MOD;
      |                  ^~
      |                  r
a.cc:77:26: error: 'MOD' was not declared in this scope
   77 |   return f[nn] * fr[r] % MOD * fr[nn - r] % MOD;
      |                          ^~~
a.cc: In function 'int main()':
a.cc:86:3: error: 'f' was not declared in this scope
   86 |   f[0] = 1;
      |   ^
a.cc:87:45: error: 'MOD' was not declared in this scope
   87 |   rrep(i, 1, n + 3) { f[i] = f[i - 1] * i % MOD; }
      |                                             ^~~
a.cc:88:3: error: 'fr' was not declared in this scope; did you mean 'fi'?
   88 |   fr[n + 2] = mod_pow(f[n + 2], MOD - 2, MOD);
      |   ^~
      |   fi
a.cc:88:33: error: 'MOD' was not declared in this scope
   88 |   fr[n + 2] = mod_pow(f[n + 2], MOD - 2, MOD);
      |                                 ^~~