The most efficient way to SUM() a series of substrings

[stonypaul]

If in column R I have a 6 digit numeric string in each cell like below what would be the most efficient way to calculate the total of the first two digits, then the 2nd two, then the 3rd two, other than using a lengthy formulae for each cell like these

=LEFT(R1,1) + MID(R1,2,1)
=MID(R1,3,1) + MID(R1,4,1)
=MID(R1,5,1) + MID(R1,6,1)

I have experimented with =SUMIF() but maybe I didn't get the syntax right. Thanks.

110001
011101
000000
111111
101010

 

[stonypaul]

=-SUMPRODUCT(-MID(R1:INDEX(R:R,COUNTA(R:R)),{1,2},1))

Assumes data is contiguous.

That almost works but the following range has a total sum of 3 instead of 5 so it looks like that only the first digit is being considered.
Also some strings commence with a 0 so there is a single speech mark to qualify the string. Is this going to confuse the formula?

111001
'011111
111111

 

[stonypaul]

=-SUMPRODUCT(-MID(R1:INDEX(R:R,COUNTA(R:R)),{1,2},1))

Assumes data is contiguous.

Thank you for your help. I tweaked your formula like this and it works as expected.

=-SUMPRODUCT(-MID(R3:INDEX(R3:R29,COUNTA(R3:R29)),{1,2},1))