ans(N) = f0(N);

f0(N) = f1(N, 0);

f1(N, C) = N == 1 ? C : f2(N, C);

f2(N, C) = N%2 == 0 ? f3(N, C) : f4(N, C);

f3(N, C) = f5(N/2, C);

f4(N, C) = f5(3*N+1, C);

f5(N, C) = f1(N, C+1);