void main(){
  import std.stdio, std.string, std.conv, std.algorithm;

  long a, c; rd(a, c);

  writeln(a^c);
}

void rd(T...)(ref T x){
  import std.stdio, std.string, std.conv;
  auto l=readln.split;
  foreach(i, ref e; x){
    e=l[i].to!(typeof(e));
  }
}