An algorithm is being developed to compress a sequence of pixel data using Run-Length Encoding (RLE).

Below is the pseudocode representation of the algorithm:

pixels ← "AAABBC"
i ← 0
run_length ← 1
WHILE i < LEN(pixels) - 1
    IF pixels[i] C1 pixels[i + 1] THEN
        OUTPUT run_length
        OUTPUT pixels[i]
        run_length ← 1
    ELSE
        run_length ← run_length + 1
    ENDIF
    i ← i + 1
ENDWHILE
OUTPUT run_length
OUTPUT pixels[i]

Which comparison operator should be placed at C1 for the algorithm to work correctly?