How many squares of different sizes can be formed by selecting several sticks from 4 sticks of 5 cm, 4 sticks of 3 cm and 4 sticks of 1 cm long and connecting them end to end.
从4根5厘米、4根3厘米和4根1厘米长的小棒中，选出若干根，并使它们首尾相接，能够摆出多少种种大小不同的正方形．
<result>7</result>