Given three kinds of weights (there are enough numbers of each) 3kg, 11kg, 17kg, how many different ways are there to combine them into 100kg (use at least one piece of each weight).
给定三种重量的砝码(每种数量都有足够多个)3kg，11kg，17kg，将它们组合凑成100kg有多少种不同的方法(每种砝码至少用一块)．
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