1. p : {1...3}
2. r : {1...3}
3. q : {1...3}
4. s : {1...3}
5. pq 6. rs Inj({1...3}; {1...3};
Inj(u.if if u=p true ; false fi r Inj(u.i; if u=q true ; false fi s Inj(u.else 6-(r+s) fi)
2 steps
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