function doukaku75r(y){
  for(var C = {}, i = y.length, c, h, t; i--;){
    h = y[i].charAt(0), t = y[i].charAt(3);
    ((c = (C[h] || (C[h] = {}))).asHead || (c.asHead = {}))[y[i]] = t;
    ((c = (C[t] || (C[t] = {}))).asTail || (c.asTail = {}))[y[i]] = h;
  }
  var CC = {}, cc, f, r;
  for(c in C) if((h = C[c].asHead) && (t = C[c].asTail)) for(r in h) for(f in t)
    (CC[cc = t[f] + h[r]] || (CC[cc] = [])).push({hitch: c, front: f, rear: r});
  var out = [], s = '　　', n = '\n', x1, x2, c1, c2;
  for(cc in CC) for(x1 in C = CC[cc]) for(x2 in C) if((c1 = C[x1]).hitch != (c2 = C[x2]).hitch)
    out[++i] = [c1.front, n,
                c2.front.charAt(1), s, c1.rear.charAt(1), n,
                c2.front.charAt(2), s, c1.rear.charAt(2), n,
                c2.rear].join('');
  return out;
}