Language: C++

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll mod = 1e9+7;
const long long INF = 1e15;

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);cout.tie(NULL);

    ll n,k;
    cin >> n >> k;
    vector<ll> p(n),c(n);

    for(ll i = 0; i < n; i++){
        cin >> p[i];
        p[i]--;
    }
    for(ll i = 0; i < n; i++) cin >> c[i];

    vector<vector<ll>> cost(n);
    vector<ll> sum(n,0);

    for(ll i = 0; i < n; i++){
        ll now = i;
        while(true){
            now = p[now];
            cost[i].push_back(c[now]);
            sum[i] += c[now];
            if(now == i) break;
        }
    }

    ll ans;
    bool first = true;

    auto calc_max = [&](ll i,ll n,bool ab){
        if(n == 0) return -1;
        ll mx = cost[i][0],tmp = 0;
        if(!ab) mx = max(0ll,mx);
        for(ll j = 0; j < n; j++){
            tmp += cost[i][j];
            mx = max(mx,tmp);
        }
        return mx;
    };


    for(ll i = 0; i < n; i++){
        ll cs = (ll)cost[i].size();
        if(sum[i] < 0){
            ll can = calc_max(i,cs,true);
            if(first){
                ans = can;
                first = false;
            } else ans = max(ans,can);
            continue;
        }
        ll can = sum[i]*(k/cs);
        ll m = k%cs;
        can += calc_max(i,m,false);
        can = max(can,calc_max(i,cs,true));
        if(first){
            ans = can;
            first = false;
        } else ans = max(ans,can);
    } 

    cout << ans << endl;
    
    return 0;
}

Compiler output:
a.cc: In lambda function:
a.cc:45:16: error: inconsistent types 'int' and 'long long int' deduced for lambda return type
   45 |         return mx;
      |                ^~
a.cc: In function 'int main()':
a.cc:62:18: error: no matching function for call to 'max(ll&, int)'
   62 |         can = max(can,calc_max(i,cs,true));
      |               ~~~^~~~~~~~~~~~~~~~~~~~~~~~~
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:62:18: note:   deduced conflicting types for parameter 'const _Tp' ('long long int' and 'int')
   62 |         can = max(can,calc_max(i,cs,true));
      |               ~~~^~~~~~~~~~~~~~~~~~~~~~~~~
/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:62:18: note:   mismatched types 'std::initializer_list<_Tp>' and 'long long int'
   62 |         can = max(can,calc_max(i,cs,true));
      |               ~~~^~~~~~~~~~~~~~~~~~~~~~~~~