算法

(模拟) $O(1)$

直接模拟即可。

C++ 代码

#include <bits/stdc++.h>

using std::cin;
using std::cout;

int main() {
    int a, b, c;
    cin >> a >> b >> c;

    if (a == b) cout << c << '\n';
    else if (a == c) cout << b << '\n';
    else if (b == c) cout << a << '\n';
    else cout << 0 << '\n';

    return 0;
}

// 更简洁的写法
#include <bits/stdc++.h>

using std::cin;
using std::cout;

int main() {
    int a, b, c;
    cin >> a >> b >> c;

    if (a != b and b != c and a != c) puts("0");
    else cout << (a ^ b ^ c) << '\n';

    return 0;
}