PLACE a1, a2, a3, a4, a5, xt, xf, yt, yf, b1, b2, b3, b4, b5, b6, b7, b8; 

MARKING a1: 1, b1: 1, xf: 1, yf: 1; 

TRANSITION t1
CONSUME b1: 1;
PRODUCE b2: 1;

TRANSITION t2
CONSUME b2: 1, yt: 1;
PRODUCE b3: 1, yt: 1; 

TRANSITION t3
CONSUME b2: 1, yf: 1;
PRODUCE b3: 1, yt: 1; 

TRANSITION t4
CONSUME b3: 1, xt: 1;
PRODUCE b4: 1, xt: 1; 

TRANSITION t5
CONSUME b3: 1, xf: 1;
PRODUCE b7: 1, xf: 1; 

TRANSITION t6
CONSUME b4: 1, yf: 1;
PRODUCE b5: 1, yf: 1; 

TRANSITION t7
CONSUME b4: 1, yt: 1;
PRODUCE b5: 1, yf: 1; 

TRANSITION t8
CONSUME b5: 1, xf: 1;
PRODUCE b6: 1, xf: 1; 

TRANSITION t9
CONSUME b5: 1, xt: 1;
PRODUCE b5: 1, xt: 1; 

TRANSITION t10
CONSUME b6: 1;
PRODUCE b2: 1;

TRANSITION t11
CONSUME b7: 1;
PRODUCE b8: 1;

TRANSITION t12
CONSUME b8: 1, yf: 1;
PRODUCE b1: 1, yf: 1; 

TRANSITION t13
CONSUME b8: 1, yt: 1;
PRODUCE b1: 1, yf: 1;