I'm trying to make a fairly simple graph, but I just can't find out how.

I have a list of donations, let's say

person amount
mary 10
john 20
carl 15
rose 30
mary 10
carl 5
john 35
rose 10
mary 20
carl 10

so I want a pie chart showing how much each person donated, but it creates a chart with 3 different marys, 2 different johns, etc.

how can I make it to group data from fields with the same name?