Python: Getting next available number

# Getting next available number. 

def getFollowingNumber(inArgs):
    ret= False;
    current= inArgs[0];
    array= inArgs[1];
    num= len(array);
    for i in range(0, num):
        if array[i]==current:
            k= current;
            j= i;
            for j in range(j, num):
                if k!=array[j]:
                    ret= k;
                    break;
                k+=1;
            break;
    if not ret: ret= current;
    return(ret);
current_number= 8; # Change this number
numberList= [0,1,2,3,4,5,8,9,10,11,12,16,17,19,20,21,23,24,25,26,28,29,31];
new_number= getFollowingNumber([current_number,numberList]);
print new_number;