So that means if the genetic code actually makes sense, then we better have 20 different unique codons that correspond to 20 different unique amino acids that appear in our body. But if we use simple math, we see that if we only have two different positions, two different nucleotides in our codon, then the maximum number of different types of codons is 16. And that's because we have four different possibilities for nucleotides. And four times four gives us 16. And 16 is not enough to actually correspond to the 20 different amino acids that exist in nature. And that's exactly why we have to add one more nucleotide so that we have three consecutive nucleotides in our codon sequence, because four times four times four gives us 64 possibilities.