a = input()
row = []
for i in a:
    row.append(i)
for i in range(len(row)):
    row[i] = int(row[i])
suml = row[0] * 100 + row[1] * 10 + row[2]
sumr = row[3] * 100 + row[4] * 10 + row[5]
if suml - sumr == 1 or sumr - suml == 1:
    print('yes')
else: print('no')