String issue (looking for the right command)(starter)

hi
i seem to have hit a wall.

a1 , a2 , a3 are (numeric or int)

a1 = 01
trace(a1)// result=1//

//i need
a1=01
a1=a1 + 1
trace(a1)// result=02//

so wd normely cuts a way the zero witch is normely very handy buth in this specific case a problem.Is there a way i can force wd to calculate on 01?
i tried to convert it to string and back to number buth that works only till 9 (and another loop in a loop will give issues)