12 times
1 c& g/ m! @4 K5.39.217.765.39.217.76" D& O4 A" x9 J1 F+ T! \
each time 4 person but 1 need to back to pick up the other 3tvb now,tvbnow,bttvb3 {7 P. D. O: f7 p( _
return x 10 = 30 peopletvb now,tvbnow,bttvb! M4 v2 a* ^( O5 h; [
1 time return% l8 y9 }$ _2 ~* S1 X) N D
2 person on last time
/ O" b2 f$ N- k2 `/ n: Itvb now,tvbnow,bttvbtotal : 12 times |