I understand the problem like that :

J - john's position
B - bomb

The first way is :
J 1 0 0
# # 2 0
B 3 0 0

So the time needed is
3 * 1.23 = 3.69

The second :
0 0 0 B
# # 2 0
J 1 0 0

Here the time
2 * 1.23 = 2.64
Total = 2.46 + 3.69 = 6.29

The third :
0 0 0 J
# # 0 1
0 0 0 B

time = 1.23
total = >>>> 7.52 <<<<< ????!!!!!

the answer in the sample isn't even a multiple of v ??!!!
WOuld You be so kind and explain it to me ??

>>So the time needed is
>>3 * 1.23 = 3.69


if move diagonal distance is sqrt(2)

(2+2*(sqrt(2)))/1.23=3.9255