Submission #70099116

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Source Code Expand

#include <bits/stdc++.h>
#ifdef LOCAL
#include <debug.hpp>
#else
#define debug(...) void(0)
#endif

template <class T, class U = T> bool chmin(T& x, U&& y) { return y < x and (x = std::forward<U>(y), true); }

template <class T, class U = T> bool chmax(T& x, U&& y) { return x < y and (x = std::forward<U>(y), true); }

template <class T> void mkuni(std::vector<T>& v) {
    std::ranges::sort(v);
    auto result = std::ranges::unique(v);
    v.erase(result.begin(), result.end());
}

template <class T> int lwb(const std::vector<T>& v, const T& x) {
    return std::distance(v.begin(), std::ranges::lower_bound(v, x));
}

using namespace std;

using ll = long long;

constexpr int MAX_LOG = 30;

void solve() {
    int C, X;
    cin >> C >> X;

    auto check = [&](int n) {
        if (n == 0) {
            return false;
        }
        return (n ^ C) % n == X;
    };
    {
        int n = X ^ C;
        if (check(n)) {
            cout << n << "\n";
            return;
        }
    }
    {
        int cur = 0, n = 1 << MAX_LOG;
        for (int i = MAX_LOG - 1, f = 1; i >= 0; i--) {
            if (C >> i & 1) {
                if (f) {
                    cur += 1 << i;
                    f = 0;
                } else {
                    if (cur < X) {
                        cur += 1 << i;
                    } else {
                        cur -= 1 << i;
                        n |= 1 << i;
                    }
                }
            }
        }
        if (check(n)) {
            cout << n << "\n";
        } else {
            cout << -1 << "\n";
        }
    }
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(15);

    int t;
    cin >> t;
    for (; t--;) {
        solve();
    }
    return 0;
}

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