Language: C++

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
typedef long long ll;

int main(){
    int n, m, k;
    cin >> n >> m >> k;
    vector<ll> 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 = 1; i <= n; i++){
        if(a[i] > k)    break;
        ans = max(ans, i+upper_bound(b.begin(),b.end(),k-a[i])-b.begin()-1);
    }
    cout << ans << endl;
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:16:18: error: no matching function for call to 'max(int&, __gnu_cxx::__normal_iterator<long long int*, std::vector<long long int> >::difference_type)'
   16 |         ans = max(ans, i+upper_bound(b.begin(),b.end(),k-a[i])-b.begin()-1);
      |               ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/string:51,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/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:16:18: note:   deduced conflicting types for parameter 'const _Tp' ('int' and '__gnu_cxx::__normal_iterator<long long int*, std::vector<long long int> >::difference_type' {aka 'long int'})
   16 |         ans = max(ans, i+upper_bound(b.begin(),b.end(),k-a[i])-b.begin()-1);
      |               ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/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,
                 from a.cc:3:
/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:16:18: note:   mismatched types 'std::initializer_list<_Tp>' and 'int'
   16 |         ans = max(ans, i+upper_bound(b.begin(),b.end(),k-a[i])-b.begin()-1);
      |               ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~