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Упражнение 15

1-on
2-on
3-at
4-at
5-at
6-at, in
7-on
8-in
9-in
10-on, in
11 at
12 at 
13 at
14 on
15at
16 at
17 on
18 in, in
19 at
20on
21at
22at
23in
24in 
25at
26at
27in
28at
29at, in, at, at
30at, on