#include <iostream>
#include <fstream>
#include <algorithm>
#include <cstring>
#include <climits>
#include <cassert>
#include <tuple>
#include <queue>
#include <stack>
#include <vector>
#include <map>
#include <set>
#include <string>
#include <unordered_set>
#include <unordered_map>
using namespace std;
typedef long long LL;
typedef vector<int> Vi;
typedef vector<LL> VL;
typedef vector<bool> Vb;
typedef vector<vector<int>> Vii;
#define forR(i, n) for (int i = 0; i < (n); i++)
int find_coin(Vi b) {
int r = 0;
forR(i, 64) {
if (b[i] == 1) {
r ^= i;
}
}
return r;
}
Vi coin_flips(Vi b, int c) {
int r = find_coin(b);
int k = c ^ r;
return Vi{ k };
}
#ifdef TEST_LOCAL
int main() {
auto result = coin_flips(Vi{ 5, 1, 1, 3, 3, 5 }, 3);
return 0;
}
#endif
