An algorithm is written in pseudo-code to calculate the shipping fee for a courier service:

1  weight ← USERINPUT
2  fee ← 8.50
3  WHILE weight > 15.0 DO
4      fee ← fee + 3.00
5      weight ← weight - 5.0
6  ENDWHILE
7  IF fee > 20.0 THEN
8      fee ← fee * 0.95
9  ENDIF
10 OUTPUT fee

Identify the line number where iteration is first used in this algorithm.