#include "bits/stdc++.h" using namespace std; #define ll long long int #define rep(i,n) for( int i = 0; i < n; i++ ) #define rrep(i,n) for( int i = n; i >= 0; i-- ) #define REP(i,s,t) for( int i = s; i <= t; i++ ) #define RREP(i,s,t) for( int i = s; i >= t; i-- ) #define dump(x) cerr << #x << " = " << (x) << endl; #define INF 2000000000 #define mod 1000000007 #define INF2 1000000000000000000 #define int long long signed main(void) { cin.tie(0); ios::sync_with_stdio(false); int A, C; cin >> A >> C; int B = A ^ C; cout << B << endl; return 0; }