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There are eight small islands in a lake, and the state wants to build seven bridges to connect them so that each island can be reached from any other one via one or more bridges. The cost of constructing a bridge is proportional to its length. The distances between pairs of islands are given in the following table.

	1	2	3	4	5	6	7	8
1	-	200	180	300	250	160	305	100
2	-	-	245	135	225	170	185	155
3	-	-	-	250	115	330	405	165
4	-	-	-	-	150	320	295	240
5	-	-	-	-	-	340	400	190
6	-	-	-	-	-	-	165	215
7	-	-	-	-	-	-	-	325
8	-	-	-	-	-	-	-	-

Find which bridges to build to minimize the total construction cost.