Problem p02623 (C++) — buggy submission, verdict: Runtime Error

#include <bits/stdc++.h>
using namespace std;
// Optimisations
#pragma GCC target("avx2")
#pragma GCC optimization("unroll-loops")
#pragma GCC optimize("O2")
// shortcuts for functions
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define all(v) v.begin(), v.end()
#define prec(n) fixed << setprecision(n)
#define n_l '\\n'
// make it python
#define gcd __gcd
#define append push_back
#define str to_string
// utility functions shortcuts
#define max3(a, b, c) max(a, max(b, c))
#define min3(a, b, c) min(a, min(b, c))
#define sswap(a, b)                                                            \\
  {                                                                            \\
    a = a ^ b;                                                                 \\
    b = a ^ b;                                                                 \\
    a = a ^ b;                                                                 \\
  }
#define swap(a, b)                                                             \\
  {                                                                            \\
    auto temp = a;                                                             \\
    a = b;                                                                     \\
    b = temp;                                                                  \\
  }
#define init(dp) memset(dp, -1, sizeof(dp));
#define set0(dp) memset(dp, 0, sizeof(dp));
#define bits(x) __builtin_popcount(x)
#define SORT(v) sort(all(v))
#define endl "\\n"
#define forr(i, n) for (ll i = 0; i < n; i++)
// declaration shortcuts
typedef long long int ll;
#define int ll
// Constants
constexpr int dx[] = {-1, 0, 1, 0, 1, 1, -1, -1};
constexpr int dy[] = {0, -1, 0, 1, 1, -1, 1, -1};
constexpr ll INF = 1999999999999999997;
constexpr int inf = INT_MAX;
constexpr int MAXSIZE = int(1e6) + 5;
constexpr auto PI = 3.14159265358979323846L;
constexpr auto oo = numeric_limits<int>::max() / 2 - 2;
constexpr auto eps = 1e-6;
constexpr auto mod = 1000000007;
constexpr auto MOD = 1000000007;
constexpr auto MOD9 = 1000000009;
constexpr auto maxn = 100006;
// void IOfile(){
// freopen(file_name, reade_mode, stdin);
// freopen(file_name, write_mode, stdout);
// }
void fastio() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
}

int a[2 * maxn];
int b[2 * maxn];

int32_t main() {
  fastio();
  int n, m, k;

  cin >> n >> m >> k;

  for (int i = 0; i < n; i++) {
    cin >> a[i];
    if (i)
      a[i] += a[i - 1];
  }
  for (int i = 0; i < m; i++) {
    cin >> b[i];
    if (i)
      b[i] += b[i - 1];
  }
  int ans1 = 0;
  for (int i = 0; i < n; i++) {
    if (a[i] <= k) {
      int left = k - a[i];
      int t = lower_bound(b, b + m, left) - b;
      if (t == 0) {
        if (b[t] == left)
          t = 1;
        ans1 = max(ans1, i + 1 + t);
      } else {
        if (b[t] == left)
          t += 1;
        ans1 = max(ans1, i + 1 + t);
      }
    }
  }

  int t = lower_bound(b, b + m, k) - b;
  if (b[t] == k)
    t += 1;
  ans1 = max(ans1, t);
  cout << ans1;
}

Error: WA

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
// Optimisations
#pragma GCC target("avx2")
#pragma GCC optimization("unroll-loops")
#pragma GCC optimize("O2")
// shortcuts for functions
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define all(v) v.begin(), v.end()
#define prec(n) fixed << setprecision(n)
#define n_l '\\n'
// make it python
#define gcd __gcd
#define append push_back
#define str to_string
// utility functions shortcuts
#define max3(a, b, c) max(a, max(b, c))
#define min3(a, b, c) min(a, min(b, c))
#define sswap(a, b)                                                            \\
  {                                                                            \\
    a = a ^ b;                                                                 \\
    b = a ^ b;                                                                 \\
    a = a ^ b;                                                                 \\
  }
#define swap(a, b)                                                             \\
  {                                                                            \\
    auto temp = a;                                                             \\
    a = b;                                                                     \\
    b = temp;                                                                  \\
  }
#define init(dp) memset(dp, -1, sizeof(dp));
#define set0(dp) memset(dp, 0, sizeof(dp));
#define bits(x) __builtin_popcount(x)
#define SORT(v) sort(all(v))
#define endl "\\n"
#define forr(i, n) for (ll i = 0; i < n; i++)
// declaration shortcuts
typedef long long int ll;
#define int ll
// Constants
constexpr int dx[] = {-1, 0, 1, 0, 1, 1, -1, -1};
constexpr int dy[] = {0, -1, 0, 1, 1, -1, 1, -1};
constexpr ll INF = 1999999999999999997;
constexpr int inf = INT_MAX;
constexpr int MAXSIZE = int(1e6) + 5;
constexpr auto PI = 3.14159265358979323846L;
constexpr auto oo = numeric_limits<int>::max() / 2 - 2;
constexpr auto eps = 1e-6;
constexpr auto mod = 1000000007;
constexpr auto MOD = 1000000007;
constexpr auto MOD9 = 1000000009;
constexpr auto maxn = 100006;
// void IOfile(){
// freopen(file_name, reade_mode, stdin);
// freopen(file_name, write_mode, stdout);
// }
void fastio() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
}

int a[maxn];
int b[maxn];

int32_t main() {
  fastio();
  int n, m, k;

  cin >> n >> m >> k;

  for (int i = 0; i < n; i++) {
    cin >> a[i];
    if (i)
      a[i] += a[i - 1];
  }
  for (int i = 0; i < m; i++) {
    cin >> b[i];
    if (i)
      b[i] += b[i - 1];
  }
  int ans1 = 0;
  for (int i = 0; i < n; i++) {
    if (a[i] <= k) {
      int left = k - a[i];
      int t = lower_bound(b, b + m, left) - b;
      if (t == 0) {
        ans1 = max(ans1, i + 1);
      } else {
        if (b[t] != left)
          t--;
        ans1 = max(ans1, i + 1 + t + 1);
      }
    }
  }

  int t = lower_bound(b, b + m, k) - b;
  ans1 = max(ans1, t);
  cout << ans1;
}