package ABC;

message A {
  optional string name = 1;
  extensions 2 to max;

  extend B { optional A keyab = 11; }
  extend C { optional A keyac = 12; }
  extend D { optional A keyad = 13; }
  extend A { optional B keyba = 14; }
  extend C { optional B keybc = 15; }
  extend D { optional B keybd = 16; }
  extend A { optional C keyca = 17; }
  extend B { optional C keycb = 18; }
  extend D { optional C keycd = 19; }
  extend A { optional D keyda = 20; }
  extend B { optional D keydb = 21; }
  extend C { optional D keydc = 22; }
}

message B {
  optional string name = 1;
  extensions 2 to max;

  extend B { optional A keyab = 111; }
  extend C { optional A keyac = 112; }
  extend D { optional A keyad = 113; }
  extend A { optional B keyba = 114; }
  extend C { optional B keybc = 115; }
  extend D { optional B keybd = 116; }
  extend A { optional C keyca = 117; }
  extend B { optional C keycb = 118; }
  extend D { optional C keycd = 119; }
  extend A { optional D keyda = 120; }
  extend B { optional D keydb = 121; }
  extend C { optional D keydc = 122; }
}


message C {
  optional string name = 1;
  extensions 2 to max;

  extend B { optional A keyab = 211; }
  extend C { optional A keyac = 212; }
  extend D { optional A keyad = 213; }
  extend A { optional B keyba = 214; }
  extend C { optional B keybc = 215; }
  extend D { optional B keybd = 216; }
  extend A { optional C keyca = 217; }
  extend B { optional C keycb = 218; }
  extend D { optional C keycd = 219; }
  extend A { optional D keyda = 220; }
  extend B { optional D keydb = 221; }
  extend C { optional D keydc = 222; }
}

message D {
  optional string name = 1;
  extensions 2 to max;

  extend B { optional A keyab = 311; }
  extend C { optional A keyac = 312; }
  extend D { optional A keyad = 313; }
  extend A { optional B keyba = 314; }
  extend C { optional B keybc = 315; }
  extend D { optional B keybd = 316; }
  extend A { optional C keyca = 317; }
  extend B { optional C keycb = 318; }
  extend D { optional C keycd = 319; }
  extend A { optional D keyda = 320; }
  extend B { optional D keydb = 321; }
  extend C { optional D keydc = 322; }
}

extend A {
  repeated B keyab = 1001;
  repeated C keyac = 1002;
  repeated D keyad = 1003;
}

extend B {
  repeated C keybc = 1011;
  repeated D keybd = 1012;
  repeated A keyba = 1013;
}

extend C {
  repeated A keyca = 1021;
  repeated B keycb = 1022;
  repeated D keycd = 1023;
}

extend D {
  repeated A keyda = 1031;
  repeated B keydb = 1032;
  repeated C keydc = 1033;
}