Check column 1 column 2 = column 3

[n3o]

i'm trying to generate a data like this

Check column 1 column 2 = column 3

1 1 Q
1 2 A
1 3 A
1 4 A
1 5 O

3 1 R
3 2 I
3 3 I
3 4 I
3 5 M

if column 1 = 1, column 2 =1 then column 3 = Q
if column 1 = 1, column 2 =2 then column 3 = A

can someone help me ... thanks