Excel Formula

I have a series of report and index table. How do i set the formula if i want to count when cell A1 = cell B1, the points = cell C1?

E.g.

ColumnA
1. ABC
2. ABC
3. GHI

ColumnB
1. ABC
2. DEF
3. GHI

ColumnC
1. 5
2. 4
3. 6