A total of 7 people took part in the banquet and a friendly handshake took place among the participants. The number of hands-on handshakes known to each of them is:
3, 1, 2, 2, 3, 1, 2
How many handshakes have occurred at the banquet?
某宴会一共有7个人参加，与会者之间进行了亲切的握手。已知他们中的每个人进行握手的次数分别为：
3, 1, 2, 2, 3, 1, 2
请问宴会上总共发生了多少次握手？
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