I need to compare two columns so that I get a TRUE value only if values in L (from row 3 down) equals values in S and both are equal to one, [but NOT if L3 is not equal to S3 OR if they are equal but contain a value other than One]

eg: i need

L S BU
1 1 YES
2 1 NO
2 2 NO
1 2 NO

i tried =IF(L3=S3=1,"YES","NO") but this answered all cells with 'NO'


i also tried all variations of that i could think of, as well as trying 'and', =IF((L3=1, S3=1),"YES","NO"), putting 1 in quotes like =IF(L3=S3="1") etc, but i can't seem to get this to work, please please help!!!