#include <bits/stdc++.h>
//#include <atcoder/all>
//using namespace atcoder;
using namespace std;

#pragma region Macros
using ll = long long;
#define int ll
using pii = pair<int, int>;
using tiii = tuple<int, int, int>;
template<class T = int> using V = vector<T>;
template<class T = int> using VV = V<V<T>>;
#define IOS\
    ios::sync_with_stdio(false);\
    cin.tie(0);\
    cout.tie(0);
#define FOR(i,l,r) for(int i=(l);i<int(r);++i)
#define REP(i,n) FOR(i,0,n)
#define REPS(i,n) FOR(i,1,n+1)
#define RFOR(i,l,r) for(int i=(l);i>=int(r);--i)
#define RREP(i,n) RFOR(i,n-1,0)
#define RREPS(i,n) RFOR(i,n,1)
#define mp make_pair
#define mt make_tuple
#define pb push_back
#define eb emplace_back
#define all(x) (x).begin(),(x).end()
#define SORT(name) sort(name.begin(), name.end())
#define RSORT(name)\
    SORT(name);\
    reverse(all(name));
#define ZERO(p) memset(p, 0, sizeof(p))
#define MINUS(p) memset(p, -1, sizeof(p))
inline void Yes(bool b = true) {cout << (b ? "Yes" : "No") << '\n';}
inline void YES(bool b = true) {cout << (b ? "YES" : "NO") << '\n';}
template <class T> inline void print(T x){ cout << x << '\n';}
template<typename T1,typename T2> inline void chmin(T1 &a, T2 b){ if(a > b) a = b; }
template<typename T1,typename T2> inline void chmax(T1 &a, T2 b){ if(a < b) a = b; }

const ll LLINF = (1LL<<60);
const int INF = (1LL<<30);
const double DINF = std::numeric_limits<double>::infinity();
#pragma endregion

const int MOD = 1000000007;

#if 1
#  define DBG(fmt, ...) printf(fmt, ##__VA_ARGS__)
#else
#  define DBG(fmt, ...)
#endif

const int MAX_N = 100010;

signed main() {
    IOS;

    int x;
    cin >> x;

    if(x < 0) { x = 0; }
    print(x);

    return 0;
}

#include "bits/stdc++.h"
using namespace std;
#define int               long long
#define pb                push_back
#define ppb               pop_back
#define pf                push_front
#define ppf               pop_front
#define all(x)            (x).begin(),(x).end()
#define uniq(v)           (v).erase(unique(all(v)),(v).end())
#define sz(x)             (int)((x).size())
#define fr                first
#define sc                second
#define pii               pair<int,int>
#define rep(i,a,b)        for(int i=a;i<b;i++)
#define mem1(a)           memset(a,-1,sizeof(a))
#define mem0(a)           memset(a,0,sizeof(a))
#define ppc               __builtin_popcount
#define ppcll             __builtin_popcountll

template<typename T1, typename T2>istream& operator>>(istream& in, pair<T1, T2> &a) {in >> a.fr >> a.sc; return in;}
template<typename T1, typename T2>ostream& operator<<(ostream& out, pair<T1, T2> a) {out << a.fr << " " << a.sc; return out;}
template<typename T, typename T1>T amax(T &a, T1 b) {if (b > a)a = b; return a;}
template<typename T, typename T1>T amin(T &a, T1 b) {if (b < a)a = b; return a;}

const long long INF = 1e18;
const int32_t M = 1e9 + 7;
const int32_t MM = 998244353;


void solve() {
	int a, b, c;
	cin >> a >> b >> c;
	if (a == b)
		cout << c;
	else if (a == c)
		cout << b;
	else if (b == c)
		cout << a;
	else
		cout << 0;
}

int32_t main() {
	ios_base::sync_with_stdio(false);
	cin.tie(0); cout.tie(0);
#ifndef ONLINE_JUDGE
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);
#endif

	int t = 1;
	// cin >> t;
	while (t--) solve();
	return 0;
}