Comparative and superlative adverbs express degrees of a quality. Comparative adverbs describe the relative qualities of two other verbs, adjectives, or adverbs. Superlative adverbs describe the relative qualities of three or more other words.
Comparative adverbs may be created by doubling the first syllable of the word:
jin (“fast”) --> jijin (“faster”)
Superlative adjectives may be created by lengthening the first vowel in the comparative:
jijin (“faster”) --> jiijin (“fastest”)
Note that this applies to short words rather than long ones. In the Northern dialect, that typically means two-syllable adverbs (which become three-syllable comparatives). The Southern dialect also allows three-syllable adverbs (which become four-syllable comparatives). The rule also works only with adverbs which begin with a consonant, because the long vowels can't appear at the beginning of a word. Others are modified by adding tote ("more") or toto ("most") after the adverb.