alphabet = "abcdefghijklmnopqrstuvwxyz0123456789 .,?!"

def let2ind(c):
    idx = 0
    for i in range(41):
        if alphabet[i] == c:
            idx = i
    return(idx)

def ind2let(n):
    if n < 41:
        return(alphabet[n])
    else:
        return(0)

    
def vEnc(c,k):
    nc = let2ind(c)
    nk = let2ind(k)
    no = (nc + nk)%41
    co = ind2let(no)
    return(co)