#include <bits/stdc++.h>

#define ll long long
#define ull unsigned long long
#define REP(a,b) for(int a=0;a<(b);++a)
#define REP1(i,n) for(int i=1;i<=(n);++i)
#define debug(x) cerr<<#x<<": "<<x<<'\n'
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define YES() printf("YES\n")
#define NO() printf("NO\n")
#define isYES(x) printf("%s\n",(x) ? "YES" : "NO")
#define Yes() printf("Yes\n")
#define No() printf("No\n")
#define isYes(x) printf("%s\n",(x) ? "Yes" : "No")
#define isPossible(x) printf("%s\n",(x) ? "Possible" : "Impossible")
#define SZ(x) ((int)(x).size())
#define pb push_back
#define mp make_pair
// #define INF (1<<9+9)
const int INF = 0x3fffffff;
// const long long INF = 1LL<<50;

#define Sp(p) cout<<setprecision(25)<< fixed<<p<<endl
#define vi vector<int>
#define vl vector<ll>
#define vii vector< vector<int> >
#define vll vector< vector<ll> >
#define vs vector<string>
#define pii pair<int,int>
#define pis pair<int,string>
#define psi pair<string,int>
#define pll pair<ll,ll>
#define pie 3.14159265358979323846

using namespace std;

typedef pair<int, int> P;
typedef pair<ll, ll> LP;
typedef pair<int, P> PP;
typedef pair<ll, LP> LPP;
template<class T=int>
T in(){T x;cin>>x;return (x);}
template<class T>
void print(T& x){cout<<x<<'\n';}

const int MOD =(int)998244353; 
// const int mod =(int)998244353;
const int mod =(int)1e9+7;

const int MAX =510000;
ll fac[MAX],finv[MAX],inv[MAX];
void COMint(){
    fac[0]=fac[1]=1;
    finv[0]=finv[1]=1;
    inv[1]=1;
    for(int i=2;i<MAX;i++){
        fac[i]=fac[i-1]*i%MOD;
        inv[i]=MOD-inv[MOD%i]*(MOD/i)%MOD;
        finv[i]=finv[i-1]*inv[i]%MOD;
    }
}
ll COM(int n,int k){
    if(n<k) return 0;
    if(n<0||k<0)return 0;
    return fac[n]*(finv[k]*finv[n-k]%MOD)%MOD;
}
ll gcd(ll a,ll b){
    if(a<0)a=-a;
    if(b<0)b=-b;
    if(b==0)return a;
    if(a>b){
        swap(a,b);
    }
    return gcd(a,b%a);
}
ll lcm(ll a,ll b){
  if(a<0)a=-a;
  if(b<0)b=-b;
    ll g;g=gcd(a,b);
    return b/g*a;
}
bool compare_by_b(pair<int, int> a, pair<int, int> b) {
    if(a.second != b.second){
        return a.second < b.second;
    }else{
        return a.first < b.first;
    }
}
bool compare_by_a(pair<int, int> a, pair<int, int> b) {
    if(a.first != b.first){
        return a.first < b.first;
    }else{
        return a.second < b.second;
    }
}
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
//int N, M, K, T, H, W, L, R;
// long long int N, M, K, T, H, W, L, R
ll RS(ll N,ll P){
    if(P==0){
        return 1;
    }else{
        if(P%2==0){
            ll t=RS(N,P/2);
            return t*t;
        }else{
            return N*RS(N,P-1);
        }
    }
}
int main() {
    ios::sync_with_stdio(false);
    int a,b,c,d;
    cin>>a>>b>>c>>d;
    cout<<b-c<<endl;
    return 0;

} 
  

#include <bits/stdc++.h>
#include <vector>
#include <iostream>
#include <map>
#include <cmath>
#include <string>
#include <algorithm>
#include <math.h>
using namespace std;

#define rep(i, o) for (int i = 0; i < (o); ++i)
#define REP(i, a, b) for (int i = (int)(a); (i) < (int)(b); i++)
#define NUM 1e5

typedef long long ll;
typedef unsigned long long ull;

ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
ll lcm(ll c, ll d) { return c / gcd(c, d) * d; }

int main()
{
    int a, b, c;
    cin >> a >> b >> c;
    int ans = 0;
    if (a == b) ans = c;
    if (b == c) ans = a;
    if (a == c) ans = b;
    cout << ans << endl;
    return 0;
}