START: DO;
       DECLARE (Y,X1,X2,X10,X20,F,F0,K1,K2,KY,EPS,
       A1,A2,B1,B2,L1,L2,LF,U,C,M,DEL) REAL;
       U=K1*X10+K2*X20-F0+KY*Y;
       IF U>M THEN U=M;
              ELSE IF U<-M THEN U=-M;
       EPS=Y-X10;
       X1=X10+DEL*(X20+B1*(U+F0)+L1*EPS );
       X2=X20+DEL*(A1*X10+A2*X20+B2*(U+F0)+L2*EPS);
       F=F0+DEL*LF*EPS;
       X10=X1;
       X20=X2;
       F0=F;
END START;

