#include <iostream>
#include <algorithm>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <bitset>
#include <cmath>

static const int MOD = 1000000007;
using ll = long long;
using u32 = unsigned;
using u64 = unsigned long long;
using namespace std;

template<class T> constexpr T INF = ::numeric_limits<T>::max()/32*15+208;

int main() {
    char a, b;
    vector<int> v(3);
    v[0] = 1;
    while(scanf(" %c,%c", &a, &b) != EOF){
        swap(v[a-'A'], v[b-'A']);
    }
    for (int i = 0; i < 3; ++i) if(v[i]) printf("%c\n", i+'A');
    return 0;
}
