plus0xxplussxyspluspsxytimes0y0timessxyplusytimespsxyexpx0s0expxsytimesxexpxyps00pssxspsxtowerxytowerIterxys0towerIter0yzztowerItersxyztowerIterpsxyexpyzplus200s1p1times2exp2tower2towerIter3FULL./TRS/Thiemann/tower.trs