import java.io.*; import java.util.*; public class Main { InputStream is; PrintWriter out; String INPUT = ""; int MOD = 1000000007; int INF = 10000000; void solve() { long a = nl(); long c = nl(); long b = 0; long p = 1; for(int i = 0; i <= 40; i++){ long x = a >> i & 1; long y = c >> i & 1; if(x != y) b += p; p *= 2; } out.println(b); } public static class UnionFind{ int parent[]; int rank[]; public UnionFind(int n){ parent = new int[n]; rank = new int[n]; for(int i = 0;i < n;i++){ parent[i] = i; rank[i] = 0; } } boolean same(int x,int y){ return find(x) == find(y); } public int find(int x){ if(parent[x] == x){ return x; }else{ return parent[x] = find(parent[x]); } } public void union(int x,int y){ x = find(x); y = find(y); if(x != y){ if(rank[x] > rank[y]){ parent[y] = x; }else{ parent[x] = y; if(rank[x] == rank[y]){ rank[y]++; } } } return; } public int count(int n){ int ret = 0; for(int i = 0;i < n;i++){ if(i == find(i)){ ret++; } } return ret; } } void run() throws Exception { is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes()); out = new PrintWriter(System.out); long s = System.currentTimeMillis(); solve(); out.flush(); if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms"); } public static void main(String[] args) throws Exception { new Main().run(); } private byte[] inbuf = new byte[1024]; private int lenbuf = 0, ptrbuf = 0; private int readByte() { if(lenbuf == -1)throw new InputMismatchException(); if(ptrbuf >= lenbuf){ ptrbuf = 0; try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); } if(lenbuf <= 0)return -1; } return inbuf[ptrbuf++]; } private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); } private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; } private double nd() { return Double.parseDouble(ns()); } private char nc() { return (char)skip(); } private String ns() { int b = skip(); StringBuilder sb = new StringBuilder(); while(!(isSpaceChar(b) && b != ' ')){ sb.appendCodePoint(b); b = readByte(); } return sb.toString(); } private char[] ns(int n) { char[] buf = new char[n]; int b = skip(), p = 0; while(p < n && !(isSpaceChar(b))){ buf[p++] = (char)b; b = readByte(); } return n == p ? buf : Arrays.copyOf(buf, p); } private char[][] nm(int n, int m) { char[][] map = new char[n][]; for(int i = 0;i < n;i++)map[i] = ns(m); return map; } private int[] na(int n) { int[] a = new int[n]; for(int i = 0;i < n;i++)a[i] = ni(); return a; } private int ni() { int num = 0, b; boolean minus = false; while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-')); if(b == '-'){ minus = true; b = readByte(); } while(true){ if(b >= '0' && b <= '9'){ num = num * 10 + (b - '0'); }else{ return minus ? -num : num; } b = readByte(); } } private long nl() { long num = 0; int b; boolean minus = false; while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-')); if(b == '-'){ minus = true; b = readByte(); } while(true){ if(b >= '0' && b <= '9'){ num = num * 10 + (b - '0'); }else{ return minus ? -num : num; } b = readByte(); } } private static void tr(Object... o) { System.out.println(Arrays.deepToString(o)); } }