Asking for advice on the summation algorithm of any two pairs

Example:
Apples: 3
Banana: 5
Watermelon: 1
Pineapple: 8
Cherry: 10

Any two fruits can be exchanged for 1 gold coin, for example, 1 apple + 1 banana = 1 gold coin, how many gold coins can be exchanged in total.

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Example:
Apples: 3
Banana: 5
Watermelon: 1
Pineapple: 8
Cherry: 10

Any two fruits can be exchanged for 1 gold coin, for example, 1 apple + 1 banana = 1 gold coin, how many gold coins can be exchanged in total.