// Time:  O(n)
// Space: O(1)

class Solution {
public:
    char findTheDifference(string s, string t) {
        return accumulate(s.cbegin(), s.cend(), 0, std::bit_xor<int>()) ^
               accumulate(t.cbegin(), t.cend(), 0, std::bit_xor<int>());
    }
};