I wanna grab the maximum value of column score for common values in first column
example
f    score
A    4
B    5
A    6
A    0
C    1
C    4
Y    2
output
f    score
A    6
B    5
C    4
Y    2
explanation: the max score when f[i]==A is 6 and when f[i]==C is 4
 
    