Language: C++

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define F first
#define S second
#define PB push_back
#define MP make_pair
#define REP(i, a, b) for (int i = a; i < b; i++)
typedef pair<ll,ll> pi;
typedef vector<ll> vi;
ll arr[200005];
ll brr[200005];
vi v;
ll n, m, k;
int main(){
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cin >> n >> m >> k;
	REP(i, 0, n){
		cin >> arr[i];
	}
	REP(i, 0, m){
		cin >> brr[i];
	}
	ll cur = 0;
	REP(i, 0, m){
		v.PB(cur);
		cur += brr[i];
	}
	v.PB(cur);
	
	ll ans = 0;
	ll x = upper_bound(v.begin(), v.end(), k) - v.begin() - 1;
	ans = max(ans, x);
	
	REP(i, 0, n){
		k -= arr[i];
		if (k < 0) break;
		ans = max(ans, i + 1 + upper_bound(v.begin(), v.end(), k) - v.begin() - 1);
	}
	cout << ans << endl;
	
}

Compiler output:
a.cc: In function 'int main()':
a.cc:39:26: error: no matching function for call to 'max(long long int&, __gnu_cxx::__normal_iterator<long long int*, std::vector<long long int> >::difference_type)'
   39 |                 ans = max(ans, i + 1 + upper_bound(v.begin(), v.end(), k) - v.begin() - 1);
      |                       ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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: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:39:26: note:   deduced conflicting types for parameter 'const _Tp' ('long long int' and '__gnu_cxx::__normal_iterator<long long int*, std::vector<long long int> >::difference_type' {aka 'long int'})
   39 |                 ans = max(ans, i + 1 + upper_bound(v.begin(), v.end(), k) - v.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:
/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:39:26: note:   mismatched types 'std::initializer_list<_Tp>' and 'long long int'
   39 |                 ans = max(ans, i + 1 + upper_bound(v.begin(), v.end(), k) - v.begin() - 1);
      |                       ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~