#include "transfer.h"
#include <bits/stdc++.h>
using namespace std;
std::vector<int> get_attachment(std::vector<int> source) {
int N = int(source.size());
int v = 0;
for (int i = 0; i < N; i++) {
v ^= source[i];
}
source.push_back(v);
vector<int> result({v});
for (int i = 0; (1 << i) < N+1; i++) {
result.push_back(0);
for (int j = 0; j < N+1; j++) {
if (j & (1 << i)) {
result.back() ^= source[j];
}
}
}
return result;
}
std::vector<int> retrieve(std::vector<int> data) {
int N;
if (data.size() == 63 + 7) {
N = 63;
} else if (data.size() == 255 + 9) {
N = 255;
} else assert(false);
vector<int> source(data.begin(), data.begin()+N);
vector<int> badAttachment = get_attachment(source);
vector<int> trueAttachment(data.begin()+N, data.end());
if (badAttachment[0] == trueAttachment[0]) {
return source;
} else {
int ind = 0;
for (int i = 0; (1 << i) < N+1; i++) {
if ((badAttachment[i+1]^1) != trueAttachment[i+1]) {
ind |= (1 << i);
}
}
if (ind < N) {
source[ind] ^= 1;
}
return source;
}
}
