Problem p02851 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;

#define lli long long int
#define REP(i, s, n) for (int i = s; i < n; i++)
#define NUM 2520
#define INF (1LL << 50)
#define DEBUG 0
#define mp(a, b) make_pair(a, b)
#define SORT(V) sort(V.begin(), V.end())
#define PI (3.141592653589794)
#define TO_STRING(VariableName) #VariableName
#define LOG(x)                                                                 \
  if (DEBUG)                                                                   \
    cout << TO_STRING(x) << "=" << x << " " << endl;
#define LOG2(x, y)                                                             \
  if (DEBUG)                                                                   \
    cout << TO_STRING(x) << "=" << x << " " << TO_STRING(y) << "=" << y << endl;
#define LOG3(x, y, z)                                                          \
  if (DEBUG)                                                                   \
    cout << TO_STRING(x) << "=" << x << " " << TO_STRING(y) << "=" << y << " " \
         << TO_STRING(z) << "=" << z << endl;
#define LOG4(w, x, y, z)                                                       \
  if (DEBUG)                                                                   \
    cout << TO_STRING(w) << "=" << w << " " << TO_STRING(x) << "=" << x << " " \
         << TO_STRING(y) << "=" << y << " " << TO_STRING(z) << "=" << z        \
         << endl;

template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}

lli sum[200100];

void func(long long N, long long K, std::vector<long long> A) {

  REP(i, 0, N) sum[i + 1] = sum[i] + A[i];
  REP(i, 0, N + 1) {
    sum[i] -= i;
    sum[i] %= K;
  }
  map<lli, lli> cnt;
  REP(i, 0, K) cnt[sum[i]]++;

  lli ans = 0;
  REP(i, 0, N + 1) {
    lli now = sum[i];
    lli c = cnt[sum[i]];
    LOG3(i, now, c);
    ans += (c - 1);
    cnt[sum[i]]--;
    if (i + K <= N)
      cnt[sum[i + K]]++;
  }
  cout << ans << endl;
}

int main() {
  // cout << fixed << setprecision(5);

  long long N;
  scanf("%lld", &N);
  long long K;
  scanf("%lld", &K);
  std::vector<long long> A(N);
  for (int i = 0; i < N; i++) {
    scanf("%lld", &A[i]);
  }
  func(N, K, std::move(A));
  return 0;
}


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

#define lli long long int
#define REP(i, s, n) for (int i = s; i < n; i++)
#define NUM 2520
#define INF (1LL << 50)
#define DEBUG 0
#define mp(a, b) make_pair(a, b)
#define SORT(V) sort(V.begin(), V.end())
#define PI (3.141592653589794)
#define TO_STRING(VariableName) #VariableName
#define LOG(x)                                                                 \
  if (DEBUG)                                                                   \
    cout << TO_STRING(x) << "=" << x << " " << endl;
#define LOG2(x, y)                                                             \
  if (DEBUG)                                                                   \
    cout << TO_STRING(x) << "=" << x << " " << TO_STRING(y) << "=" << y << endl;
#define LOG3(x, y, z)                                                          \
  if (DEBUG)                                                                   \
    cout << TO_STRING(x) << "=" << x << " " << TO_STRING(y) << "=" << y << " " \
         << TO_STRING(z) << "=" << z << endl;
#define LOG4(w, x, y, z)                                                       \
  if (DEBUG)                                                                   \
    cout << TO_STRING(w) << "=" << w << " " << TO_STRING(x) << "=" << x << " " \
         << TO_STRING(y) << "=" << y << " " << TO_STRING(z) << "=" << z        \
         << endl;

template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}

lli sum[200100];

void func(long long N, long long K, std::vector<long long> A) {

  REP(i, 0, N) sum[i + 1] = sum[i] + A[i];
  REP(i, 0, N + 1) {
    sum[i] -= i;
    sum[i] %= K;
  }
  map<lli, lli> cnt;
  REP(i, 0, min(K, N + 1)) cnt[sum[i]]++;

  lli ans = 0;
  REP(i, 0, N + 1) {
    lli now = sum[i];
    lli c = cnt[sum[i]];
    LOG3(i, now, c);
    ans += (c - 1);
    cnt[sum[i]]--;
    if (i + K <= N)
      cnt[sum[i + K]]++;
  }
  cout << ans << endl;
}

int main() {
  // cout << fixed << setprecision(5);

  long long N;
  scanf("%lld", &N);
  long long K;
  scanf("%lld", &K);
  std::vector<long long> A(N);
  for (int i = 0; i < N; i++) {
    scanf("%lld", &A[i]);
  }
  func(N, K, std::move(A));
  return 0;
}