Language: C++

// Sky's the limit :)
#include <bits/stdc++.h>
using namespace std;
#define int long long

signed main() {
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    
    int T = 1; 
    // cin >> T; 
    while (T--) {
        int n, m, k;
        cin >> n >> m >> k;
        vector<int> a(n + 1, 0), b(m + 1, 0);
        for(int i = 1; i <= n; i++) {
            cin >> a[i];
            a[i] += a[i - 1];
        }
        for(int i = 1; i <= m; i++) {
            cin >> b[i];
            b[i] += b[i - 1];
        }

        int ans = 0;
        for(int i = 0; i <= n; i++) {
            int rem = k - a[i];
            if(rem < 0)
                break;
            auto pos = max(--upper_bound(b.begin(), b.end(), rem) - b.begin(), 0LL);
            // cout << i << ' ' << rem << ' ' << pos << '\n';
            ans = max(ans, i + pos);
        }

        cout << ans << '\n';
        
    }
    
    return 0;
}



Compiler output:
a.cc: In function 'int main()':
a.cc:29:27: error: no matching function for call to 'max(__gnu_cxx::__normal_iterator<long long int*, std::vector<long long int> >::difference_type, long long int)'
   29 |             auto pos = max(--upper_bound(b.begin(), b.end(), rem) - b.begin(), 0LL);
      |                        ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 from a.cc:2:
/usr/include/c++/14/bits/stl_algobase.h:257:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::max(const _Tp&, const _Tp&)'
  257 |     max(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:257:5: note:   template argument deduction/substitution failed:
a.cc:29:27: note:   deduced conflicting types for parameter 'const _Tp' ('long int' and 'long long int')
   29 |             auto pos = max(--upper_bound(b.begin(), b.end(), rem) - b.begin(), 0LL);
      |                        ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::max(const _Tp&, const _Tp&, _Compare)'
  303 |     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/algorithm:61:
/usr/include/c++/14/bits/stl_algo.h:5706:5: note: candidate: 'template<class _Tp> constexpr _Tp std::max(initializer_list<_Tp>)'
 5706 |     max(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5706:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5716:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::max(initializer_list<_Tp>, _Compare)'
 5716 |     max(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5716:5: note:   template argument deduction/substitution failed:
a.cc:29:27: note:   mismatched types 'std::initializer_list<_Tp>' and 'long int'
   29 |             auto pos = max(--upper_bound(b.begin(), b.end(), rem) - b.begin(), 0LL);
      |                        ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~