Language: C++

#include"bits/stdc++.h"
using namespace std;

#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)
#define rep3(i,m,n) for(int (i)=m;(i)<=(n);(i)++)
#define rep3rev(i,m,n) for(int (i)=m;(i)>=(n);(i)--)
#define all(a) (a.begin()),(a.end())
#define rall(a) (a.rbegin()),(a.rend())
#define fi first
#define se second
#define pb push_back
#define eb emplace_back

using ll = long long;
using vll = vector<ll>;
using vi = vector<int>;
using vvi = vector<vector<int>>;
using P = pair<int, int>;

void Main(){
    int n, m, k; cin >> n >> m >> k;
    vll a(n), suma(n+1, 0); 
    rep(i, n) {
        cin >> a[i];
        suma[i+1] = suma[i] + a[i];
    }
    vll b(m), sumb(m+1, 0);
    rep(i, m) {
        cin >> b[i];
        sumb[i+1] = sumb[i] + b[i];
    }
    
    int kk;
    ll mx = 0;
    
    rep(i, n+1){
        kk = k;
        kk -= suma[i];
        if(kk <= 0) break;
        auto it = upper_bound(all(sumb), kk);
        it--;
        int tmp = it - sumb.begin();
        int ans = i + tmp;
        mx = max(mx, ans);
    }
    
    cout << mx << endl;    
	return;
}

int main(){
	cin.tie(nullptr);
	ios_base::sync_with_stdio(false);
	cout << fixed << setprecision(15);
	Main();
	return 0;
}

Compiler output:
a.cc: In function 'void Main()':
a.cc:44:17: error: no matching function for call to 'max(ll&, int&)'
   44 |         mx = max(mx, ans);
      |              ~~~^~~~~~~~~
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:44:17: note:   deduced conflicting types for parameter 'const _Tp' ('long long int' and 'int')
   44 |         mx = max(mx, ans);
      |              ~~~^~~~~~~~~
/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:44:17: note:   mismatched types 'std::initializer_list<_Tp>' and 'long long int'
   44 |         mx = max(mx, ans);
      |              ~~~^~~~~~~~~