| Count | Prefix |
|---|---|
| 336 | ff- |
| 19 | ff. |
| 13 | ff0 |
| 42 | ff1 |
| 21 | ff2 |
| 17 | ff3 |
| 18 | ff4 |
| 8 | ff5 |
| 13 | ff6 |
| 12 | ff7 |
| 12 | ff8 |
| 14 | ff9 |
| 361 | ffa |
| 191 | ffb |
| 374 | ffc |
| 123 | ffd |
| 214 | ffe |
| 296 | fff |
| 163 | ffg |
| 107 | ffh |
| 254 | ffi |
| 43 | ffj |
| 63 | ffk |
| 205 | ffl |
| 242 | ffm |
| 97 | ffn |
| 186 | ffo |
| 184 | ffp |
| 12 | ffq |
| 187 | ffr |
| 286 | ffs |
| 194 | fft |
| 83 | ffu |
| 61 | ffv |
| 162 | ffw |
| 66 | ffx |
| 31 | ffy |
| 29 | ffz |