rt。

#include <bits/stdc++.h>
#pragma GCC optimize(3, "Ofast", "inline")
using namespace std;

unsigned long long n, m, K, ans, now, cost;
bool flag;
array<unsigned long long, 200001> a;

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    cin >> n >> m >> K;
    auto B(a.begin()), E(a.begin() + n), F(a.begin() + K);
    for(auto i(B); i != E; ++ i)
        cin >> *i;
    sort(B, E, greater<unsigned long long>());
    for(unsigned long long j(2147483648ull); j; j >>= 1ull)
    {
        now = cost = 0ull;
        for(auto i(B); i != E; ++ i)
            if(*i & j && now < K)
                ++ now;
            else if(i < F)
                cost -= *i;
        cost += j * (K - now);
        if(m >= cost)
        {
            m -= cost;
            flag = true;
            ans = j;
            for(auto i(B); i != F; ++ i)
                if(! (*i & j))
                    *i = 0ull;
        }
        else
            flag = false;
        for(auto i(B); i != E; ++ i)
        {
            *i |= j;
            *i ^= j;
        }
        if(flag)
            break;
        sort(B, E, greater<unsigned long long>());
    }
    sort(B, F, greater<unsigned long long>());
    for(unsigned long long j(ans >> 1u); j; j >>= 1ull)
    {
        now = cost = 0ull;
        for(auto i(B); i != F; ++ i)
            if(*i & j)
                ++ now;
            else
                cost -= *i;
        cost += j * (K - now);
        if(m >= cost)
        {
            m -= cost;
            ans |= j;
            for(auto i(B); i != F; ++ i)
                if(! (*i & j))
                    *i = 0ull;
        }
        for(auto i(B); i != F; ++ i)
        {
            *i |= j;
            *i ^= j;
        }
        sort(B, F, greater<unsigned long long>());
    }
    cout << ans;
    return 0;
}