how many teams were in the league when bill russel played

Bill Russell played 13 seasons for the Celtics. He averaged 22.5 rebounds, 15.1 points and 4.3 assists in 963 regular-season games. He was selected to play in 12 All-Star games. He won 5 MVP awards and 11 NBA championships. He was inducted into the Hall of Fame in 1975.

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How many teams were in the league when bill russel played in his career?

	NAME	SEASON	TM	GP	MPG	PPG	RPG	APG	FGM	FGA	FG%	FTM	FTA	FT%	TS%	MIN	PTS	REB	AST	PF
1	Bill Russell B. Russell	1956-57	BOS	48	35.3	14.7	19.6	1.8	5.8	13.5	42.7	3.2	6.4	49.2	45.0	1,695	706	943	88	143
2	Bill Russell B. Russell	1957-58	BOS	69	38.3	16.6	22.7	2.9	6.6	15.0	44.2	3.3	6.4	51.9	46.5	2,640	1,142	1,564	202	181
3	Bill Russell B. Russell	1958-59	BOS	70	42.6	16.7	23.0	3.2	6.5	14.2	45.7	3.7	6.1	59.8	49.3	2,979	1,168	1,612	222	161
4	Bill Russell B. Russell	1959-60	BOS	74	42.5	18.2	24.0	3.7	7.5	16.1	46.7	3.2	5.3	61.2	49.6	3,146	1,350	1,778	277	210
5	Bill Russell B. Russell	1960-61	BOS	78	44.3	16.9	23.9	3.4	6.8	16.0	42.6	3.3	6.0	55.0	45.4	3,458	1,322	1,868	268	155
6	Bill Russell B. Russell	1961-62	BOS	76	45.2	18.9	23.6	4.5	7.6	16.6	45.7	3.8	6.3	59.5	48.9	3,433	1,436	1,790	341	207
7	Bill Russell B. Russell	1962-63	BOS	78	44.9	16.8	23.6	4.5	6.6	15.2	43.2	3.7	6.6	55.5	46.4	3,500	1,309	1,843	348	189
8	Bill Russell B. Russell	1963-64	BOS	78	44.6	15.0	24.7	4.7	6.0	13.8	43.3	3.0	5.5	55.0	46.1	3,482	1,168	1,930	370	190
9	Bill Russell B. Russell	1964-65	BOS	78	44.4	14.1	24.1	5.3	5.5	12.6	43.8	3.1	5.5	57.3	47.2	3,466	1,102	1,878	410	204
10	Bill Russell B. Russell	1965-66	BOS	78	43.4	12.9	22.8	4.8	5.0	12.1	41.5	2.9	5.2	55.1	44.8	3,386	1,005	1,779	371	221
11	Bill Russell B. Russell	1966-67	BOS	81	40.7	13.3	21.0	5.8	4.9	10.7	45.4	3.5	5.8	61.0	50.0	3,297	1,075	1,700	472	258
12	Bill Russell B. Russell	1967-68	BOS	78	37.9	12.5	18.6	4.6	4.7	11.0	42.5	3.2	5.9	53.7	46.1	2,953	977	1,451	357	242
13	Bill Russell B. Russell	1968-69	BOS	77	42.7	9.9	19.3	4.9	3.6	8.4	43.3	2.6	5.0	52.6	46.7	3,291	762	1,484	374	231
	Average			74.1	42.3	15.1	22.5	4.3	5.9	13.4	44.0	3.3	5.8	56.1	47.1	3132.8	1117.1	1663.1	315.4	199.4
	Total			963	42.3	15.1	22.5	4.3	5.9	13.4	44.0	3.3	5.8	56.1	47.1	40,726	14,522	21,620	4,100	2,592