#include <bits/stdc++.h>
#include <atcoder/all>

using namespace std;

//#define DISABLE_PRINT

#if defined(ENABLE_PRINT) && !defined(DISABLE_PRINT)

#define P(...) fprintf(stderr, __VA_ARGS__)
#define P2(fmt) fprintf(stderr, fmt)
#define LP fprintf(stderr, "L: %d\n", __LINE__)

#else

#define P(...) ((void)0)
#define P2(fmt) ((void)0)
#define LP ((void)0)

#endif

#define rep(i, n) for(int i = 0; i < (int)(n); ++i)
#define ALL(x) x.begin(),x.end()

using ll = long long;
using ull = unsigned long long;

int main(int, const char**)
{
    int a, b, c; cin >> a >> b >> c;
    if(a != b && a != c && b != c) {
        bool found[4]{};
        found[a] = true;
        found[b] = true;
        found[c] = true;
        rep(i, 4) {
            if(!found[i]) {
                cout << i << endl;
                return 0;
            }
        }
    }
    if(a == b && b == c) {
        cout << a << endl;
        return 0;
    }

    map<int, int> m;
    m[a]++;
    m[b]++;
    m[c]++;
    for(auto p : m) {
        if(p.second == 1) {
            cout << p.first << endl;
        }
    }
    return 0;
}