"CODE" 33013 ;
   "PROCEDURE" RK2N(X, A, B, Y, YA, Z, ZA, FXYZJ, J, E, D,
   FI, N); "VALUE" B, FI, N; "INTEGER" J, N; "REAL" X, A, B, FXYZJ;
   "BOOLEAN" FI; "ARRAY" Y, YA, Z, ZA, E, D;
   "BEGIN" "INTEGER" JJ;
      "REAL" XL, H, INT, HMIN, HL, ABSH, FHM, DISCRY, DISCRZ,
      TOLY, TOLZ, MU, MU1, FHY, FHZ;
      "BOOLEAN" LAST, FIRST, REJECT;
      "ARRAY" YL, ZL, K0, K1, K2, K3, K4, K5[1:N], EE[1:4 *
      N];
      "IF" FI "THEN"
      "BEGIN" D[3]:= A;
         "FOR" JJ:= 1 "STEP" 1 "UNTIL" N "DO"
         "BEGIN" D[JJ + 3]:= YA[JJ]; D[N + JJ + 3]:= ZA[JJ]
         "END"
      "END";
      D[1]:= 0; XL:= D[3];
      "FOR" JJ:= 1 "STEP" 1 "UNTIL" N "DO"
      "BEGIN" YL[JJ]:= D[JJ + 3]; ZL[JJ]:= D[N + JJ + 3] "END";
      "IF" FI "THEN" D[2]:= B - D[3]; ABSH:= H:= ABS(D[2]);
      "IF" B - XL < 0 "THEN" H:= - H; INT:= ABS(B - XL);
      HMIN:= INT * E[1] + E[2];
      "FOR" JJ:= 2 "STEP" 1 "UNTIL" 2 * N "DO"
      "BEGIN" HL:= INT * E[2 * JJ - 1] + E[2 * JJ];
         "IF" HL < HMIN "THEN" HMIN:= HL
      "END";
      "FOR" JJ:= 1 "STEP" 1 "UNTIL" 4 * N "DO" EE[JJ]:= E[JJ] / INT;
      FIRST:= "TRUE"; "IF" FI "THEN"
      "BEGIN" LAST:= "TRUE"; "GOTO" STEP "END";
   TEST: ABSH:= ABS(H); "IF" ABSH < HMIN "THEN"
      "BEGIN" H:= "IF" H > 0 "THEN" HMIN "ELSE" - HMIN;
         ABSH:= ABS(H)
      "END";
      "IF" H >= B - XL "EQV" H >= 0 "THEN"
      "BEGIN" D[2]:= H; LAST:= "TRUE"; H:= B - XL;
         ABSH:= ABS(H)
      "END"
      "ELSE" LAST:= "FALSE";
   STEP: X:= XL;
      "FOR" JJ:= 1 "STEP" 1 "UNTIL" N "DO"
      "BEGIN" Y[JJ]:= YL[JJ]; Z[JJ]:= ZL[JJ] "END";
      "FOR" J:= 1 "STEP" 1 "UNTIL" N "DO" K0[J]:= FXYZJ * H;
      X:= XL + H / 4.5;
      "FOR" JJ:= 1 "STEP" 1 "UNTIL" N "DO"
      "BEGIN" Y[JJ]:= YL[JJ] + (ZL[JJ] * 18 + K0[JJ] * 2) /
         81 * H; Z[JJ]:= ZL[JJ] + K0[JJ] / 4.5;
      "FOR" J:= 1 "STEP" 1 "UNTIL" N "DO" K1[J]:= FXYZJ * H;
      X:= XL + H / 3;
      "FOR" JJ:= 1 "STEP" 1 "UNTIL" N "DO"
      "BEGIN" Y[JJ]:= YL[JJ] + (ZL[JJ] * 6 + K0[JJ]) / 18 * H;
         Z[JJ]:= ZL[JJ] + (K0[JJ] + K1[JJ] * 3) / 12
      "END";
      "FOR" J:= 1 "STEP" 1 "UNTIL" N "DO" K2[J]:= FXYZJ * H;
      X:= XL + H * .5;
      "FOR" JJ:= 1 "STEP" 1 "UNTIL" N "DO"
      "BEGIN" Y[JJ]:= YL[JJ] + (ZL[JJ] * 8 + K0[JJ] + K2[JJ])
         / 16 * H;
         Z[JJ]:= ZL[JJ] + (K0[JJ] + K2[JJ] * 3) / 8
      "END";
      "FOR" J:= 1 "STEP" 1 "UNTIL" N "DO" K3[J]:= FXYZJ * H;
      X:= XL + H * .8;
      "FOR" JJ:= 1 "STEP" 1 "UNTIL" N "DO"
      "BEGIN" Y[JJ]:= YL[JJ] + (ZL[JJ] * 100 + K0[JJ] * 12 +
         K3[JJ] * 28) / 125 * H;
         Z[JJ]:= ZL[JJ] + (K0[JJ] * 53 - K1[JJ] * 135 +
         K2[JJ] * 126 + K3[JJ] * 56) / 125
      "END";
      "FOR" J:= 1 "STEP" 1 "UNTIL" N "DO" K4[J]:= FXYZJ * H;
      X:= "IF" LAST "THEN" B "ELSE" XL + H;
      "FOR" JJ:= 1 "STEP" 1 "UNTIL" N "DO"
      "BEGIN" Y[JJ]:= YL[JJ] + (ZL[JJ] * 336 + K0[JJ] * 21 +
         K2[JJ] * 92 + K4[JJ] * 55) / 336 * H;
         Z[JJ]:= ZL[JJ] + (K0[JJ] * 133 - K1[JJ] * 378 +
         K2[JJ] * 276 + K3[JJ] * 112 + K4[JJ] * 25) / 168
      "END";
      "FOR" J:= 1 "STEP" 1 "UNTIL" N "DO" K5[J]:= FXYZJ * H;
      REJECT:= "FALSE"; FHM:= 0;
      "FOR" JJ:= 1 "STEP" 1 "UNTIL" N "DO"
      "BEGIN" DISCRY:= ABS(( - K0[JJ] * 21 + K2[JJ] * 108 -
         K3[JJ] * 112 + K4[JJ] * 25) / 56 * H);
         DISCRZ:= ABS(K0[JJ] * 21 - K2[JJ] * 162 + K3[JJ]
         * 224 - K4[JJ] * 125 + K5[JJ] * 42) / 14;
         TOLY:= ABSH * (ABS(ZL[JJ]) * EE[2 * JJ - 1] +
         EE[2 * JJ]);
         TOLZ:= ABS(K0[JJ]) * EE[2 * (JJ + N) - 1] + ABSH
         * EE[2 * (JJ + N)];
         REJECT:= DISCRY > TOLY "OR" DISCRZ > TOLZ "OR" REJECT;
         FHY:= DISCRY / TOLY; FHZ:= DISCRZ / TOLZ;
         "IF" FHZ > FHY "THEN" FHY:= FHZ;
         "IF" FHY > FHM "THEN" FHM:= FHY
      MU:= 1 / (1 + FHM) + .45; "IF" REJECT "THEN"
      "BEGIN" "IF" ABSH <= HMIN "THEN"
         "BEGIN" D[1]:= D[1] + 1;
            "FOR" JJ:= 1 "STEP" 1 "UNTIL" N "DO"
            "BEGIN" Y[JJ]:= YL[JJ]; Z[JJ]:= ZL[JJ] "END";
            FIRST:= "TRUE"; "GOTO" NEXT
         "END";
         H:= MU * H; "GOTO" TEST
      "END";
      "IF" FIRST "THEN"
      "BEGIN" FIRST:= "FALSE"; HL:= H; H:= MU * H; "GOTO" ACC
      "END";
      FHM:= MU * H / HL + MU - MU1; HL:= H; H:= FHM * H;
   ACC: MU1:= MU;
      "FOR" JJ:= 1 "STEP" 1 "UNTIL" N "DO"
      "BEGIN" Y[JJ]:= YL[JJ] + (ZL[JJ] * 56 + K0[JJ] * 7 +
         K2[JJ] * 36 - K4[JJ] * 15) / 56 * HL;
         Z[JJ]:= ZL[JJ] + ( - K0[JJ] * 63 + K1[JJ] * 189
         - K2[JJ] * 36 - K3[JJ] * 112 + K4[JJ] * 50) / 28
      "END";
      "FOR" J:= 1 "STEP" 1 "UNTIL" N "DO" K5[J]:= FXYZJ * HL;
      "FOR" JJ:= 1 "STEP" 1 "UNTIL" N "DO"
      "BEGIN" Y[JJ]:= YL[JJ] + (ZL[JJ] * 336 + K0[JJ] * 35 +
         K2[JJ] * 108 + K4[JJ] * 25) / 336 * HL;
         Z[JJ]:= ZL[JJ] + (K0[JJ] * 35 + K2[JJ] * 162 +
         K4[JJ] * 125 + K5[JJ] * 14) / 336
      "END";
   NEXT: "IF" B ^= X "THEN"
      "BEGIN" XL:= X;
         "FOR" JJ:= 1 "STEP" 1 "UNTIL" N "DO"
         "BEGIN" YL[JJ]:= Y[JJ]; ZL[JJ]:= Z[JJ] "END";
         "GOTO" TEST
      "END";
      "IF" "NOT"LAST "THEN" D[2]:= H; D[3]:= X;
      "FOR" JJ:= 1 "STEP" 1 "UNTIL" N "DO"
      "BEGIN" D[JJ + 3]:= Y[JJ]; D[N + JJ + 3]:= Z[JJ] "END"
   "END" RK2N;
        "EOP"