#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;

#define rep(i, n) REP(i, 0, n)
#define ALL(v) v.begin(), v.end()
#define MSG(a) cout << #a << " " << a << endl;
#define REP(i, x, n) for (int i = x; i < n; i++)
#define OP(m) cout << m << endl
typedef long long ll;
typedef unsigned long long ull;

int main()
{
    map<char, bool> boll = {{'A', 1}, {'B', 0}, {'C', 0}};
    char c, d, e;
    char ans = 'A';
    while (cin >> c >> d >> e)
    {
        if (boll[c] == 1)
        {
            ans = e;
        }
        else if (boll[e] == 1)
        {
            ans = c;
        }
        swap(boll[c], boll[e]);
    }

    OP(ans);
    return 0;
}
