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

#include "bits/stdc++.h"
#include "ext/pb_ds/assoc_container.hpp"
#include "ext/pb_ds/tree_policy.hpp"
#define ordered_set                                                            \\
  tree<pair<int, int>, null_type, less<pair<int, int>>, rb_tree_tag,           \\
       tree_order_statistics_node_update>
using namespace std;
using namespace __gnu_pbds;
#define int long long int
#define pb push_back
#define vec vector<int>
#define fo(i, n) for (int i = 0; i < n; i++)
#define foo(i, a, b) for (int i = a; i < b; i++)
#define mp make_pair
#define deb(x) cout << #x << " --> " << x << endl;
#define deb1a(v)                                                               \\
  cout << #v << "--->" << endl;                                                \\
  for (auto it : v)                                                            \\
    cout << it << " ";                                                         \\
  cout << endl;
#define deb2a(v)                                                               \\
  cout << #v << "--->" << endl;                                                \\
  for (auto it : v) {                                                          \\
    for (auto it1 : it) {                                                      \\
      cout << it1 << " ";                                                      \\
    }                                                                          \\
    cout << endl;                                                              \\
  }
#define deb3a(v)                                                               \\
  cout << #v << "-->" << endl;                                                 \\
  for (auto it : v) {                                                          \\
    cout << it.fi << " " << it.se << endl;                                     \\
  }
#define mod 1000000007
#define so(v) sort(v.begin(), v.end())
#define fi first
#define se second
#define db1(x) cout << #x << "=" << x << endl
#define db2(x, y) cout << #x << "=" << x << "," << #y << "=" << y << endl
#define db3(x, y, z)                                                           \\
  cout << #x << "=" << x << "," << #y << "=" << y << "," << #z << "=" << z     \\
       << endl
int power(int x, unsigned int y, int p) {
  int res = 1;
  x = x % p;
  while (y > 0) {
    if (y & 1)
      res = (res * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return res;
}
int mI(int a, int m) { return power(a, m - 2, m); }
vector<vector<int>> dir = {{0, 1}, {0, -1}, {1, 0},  {-1, 0},
                           {1, 1}, {1, -1}, {-1, 1}, {-1, -1}};

void solve() {
  int n, m, k;
  cin >> n >> m >> k;
  vec a(n), b(m);
  int ans = 0;
  fo(i, n) { cin >> a[i]; }
  fo(i, m) { cin >> b[i]; }
  if (a[0] <= k) {
    ans = 1;
  }
  foo(i, 1, n) {
    a[i] += a[i - 1];
    if (a[i] <= k) {
      ans = max(ans, i + 1);
    }
  }
  if (b[0] <= k) {
    ans = max(ans, (int)1);
  }
  foo(i, 1, m) {
    b[i] += b[i - 1];
    if (b[i] <= k) {
      ans = max(ans, i + 1);
    }
  }
  fo(i, n) {
    if (a[i] > k) {
      break;
    }
    auto it = upper_bound(b.begin(), b.end(), k - a[i]) - b.begin();
    if (it == 0) {
      break;
    } else {
      ans = max(ans, i + 1 + it);
    }
  }
  cout << ans;
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int t = 1;
  // cin >> t;

  while (t--) {
    solve();
  }
}


Error: WA

Fixed submission:

#include "bits/stdc++.h"
#include "ext/pb_ds/assoc_container.hpp"
#include "ext/pb_ds/tree_policy.hpp"
#define ordered_set                                                            \\
  tree<pair<int, int>, null_type, less<pair<int, int>>, rb_tree_tag,           \\
       tree_order_statistics_node_update>
using namespace std;
using namespace __gnu_pbds;
#define int long long int
#define pb push_back
#define vec vector<int>
#define fo(i, n) for (int i = 0; i < n; i++)
#define foo(i, a, b) for (int i = a; i < b; i++)
#define mp make_pair
#define deb(x) cout << #x << " --> " << x << endl;
#define deb1a(v)                                                               \\
  cout << #v << "--->" << endl;                                                \\
  for (auto it : v)                                                            \\
    cout << it << " ";                                                         \\
  cout << endl;
#define deb2a(v)                                                               \\
  cout << #v << "--->" << endl;                                                \\
  for (auto it : v) {                                                          \\
    for (auto it1 : it) {                                                      \\
      cout << it1 << " ";                                                      \\
    }                                                                          \\
    cout << endl;                                                              \\
  }
#define deb3a(v)                                                               \\
  cout << #v << "-->" << endl;                                                 \\
  for (auto it : v) {                                                          \\
    cout << it.fi << " " << it.se << endl;                                     \\
  }
#define mod 1000000007
#define so(v) sort(v.begin(), v.end())
#define fi first
#define se second
#define db1(x) cout << #x << "=" << x << endl
#define db2(x, y) cout << #x << "=" << x << "," << #y << "=" << y << endl
#define db3(x, y, z)                                                           \\
  cout << #x << "=" << x << "," << #y << "=" << y << "," << #z << "=" << z     \\
       << endl
int power(int x, unsigned int y, int p) {
  int res = 1;
  x = x % p;
  while (y > 0) {
    if (y & 1)
      res = (res * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return res;
}
int mI(int a, int m) { return power(a, m - 2, m); }
vector<vector<int>> dir = {{0, 1}, {0, -1}, {1, 0},  {-1, 0},
                           {1, 1}, {1, -1}, {-1, 1}, {-1, -1}};

void solve() {
  int n, m, k;
  cin >> n >> m >> k;
  vec a(n), b(n);
  int ans = 0;
  fo(i, n) { cin >> a[i]; }
  fo(i, m) { cin >> b[i]; }
  foo(i, 1, n) { a[i] += a[i - 1]; }
  foo(i, 1, m) { b[i] += b[i - 1]; }
  fo(i, n) {
    auto it = upper_bound(b.begin(), b.end(), k) - b.begin();
    { ans = max(ans, (int)it); }
    if (a[i] > k) {
      break;
    }
    it = upper_bound(b.begin(), b.end(), k - a[i]) - b.begin();
    { ans = max(ans, i + 1 + it); }
  }
  cout << ans;
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int t = 1;
  // cin >> t;

  while (t--) {
    solve();
  }
}