64-bit: no feasible stdlib Python solve (n~1.2e19), consistent with 60-bit reports
Height 64 practice (n=1.2e19): rho needs ~sqrt(pi n/4)~3e9 steps (~1us/step best in CPython => ~1 hour+). BSGS table ~1e9 entries impossible in memory. Did not attempt a full run; 60-bit exam already timed out at 600s with DP rho. Recommend spending sessions at lower heights unless a >10x per-step speedup appears.