code 41023;
real procedure RUN(X, M, N);
value X, M, N; real X, M, N;
begin
    real P, PCUM; integer IX, I, K, UP;
    if M < 0 ∨ ENTIER(M) < M then
    STATAL3 ERROR(“RUN”, 2, M) else
    if N < 0 ∨ ENTIER(N) < N then
    STATAL3 ERROR(“RUN”, 3, N) else
    if M > N then begin K:= M; M:= N; N:= K end;
    if M = 0 then RUN:= (if X < 1 then 0 else 1)
    else if X < 2 then RUN:= 0 else
    if M = N ∧ X ≥ M × 2 then RUN:= 1 else
    if X > M × 2 then RUN:= 1 else
    begin IX:= ENTIER(X); if IX ÷ 2 × 2 < IX then
        begin PCUM:= P:= RUNPROB(IX, M, N);
                 K:= (IX - 1) / 2;
                 P:= P×K×2 / (M + N - K × 2); PCUM:= PCUM + P
             end else
             begin K:= IX / 2;
                 P:= PCUM:= RUNPROB(IX, M, N)
             end;
          for I:= K - 1 step -1 until 1 do
          begin P:= P × (M + N - I × 2) × I / (N - I) /
              (M - I) / 2; PCUM:= PCUM + P;
              P:= P×2×I / (M + N - 2 × I); PCUM:= PCUM + P
          end;
          RUN:= PCUM
      end
end RUN;
eop