import sys

s = 'abcdefghijklmnopqrstuvwxyz.?! '
d = {}
for y in range(1, 7):
    for t in range(1, 6):
        d[(str(y),str(t))] = s[0]
        s = s[1:]

for line in sys.stdin:
    line = line.rstrip()
    if len(line) == 0 or len(line) % 2 != 0:
        print 'NA'
        continue
    ans = ''
    for i in range(0, len(line), 2):
        if d[(line[i],line[i+1])]:
            ans += d[(line[i],line[i+1])]
        else:
            print 'NA'
            break
    else:
        print ans