AOJ 2527 MLE.cpp

#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define rep(i,n) for(ll i=0;i<(ll)(n);i++)
#define all(a)  (a).begin(),(a).end()
#define pb emplace_back
 
ll bucket[1<<16];
 
int main() {
    int n,k,x0;
    cin>>n>>k>>x0;
    k--;
     
    if(x0==0){
        cout<<0<<endl;
        return 0;
    }
 
    ull x = x0;
    rep(i,n){
        bucket[uint16_t((x>>(64-16)) + (1<<15))]++;
        x ^= x<<13;
        x ^= x>>7;
        x ^= x<<17;
    }
 
    ll key;
    for(key=0;k-bucket[key]>=0;key++){
        k-=bucket[key];
    }
 
    vector<ll> v;
    x = x0;
    rep(i,n){
        if(uint16_t((x>>(64-16)) + (1<<15))==key){
            v.pb(x);
        }
        x ^= x<<13;
        x ^= x>>7;
        x ^= x<<17;
    }
 
    sort(all(v));
    cout<<v[k]<<endl;
}