INF = 10 ** 9
MOD = 10 ** 9 + 7
import sys
sys.setrecursionlimit(100000000)
dy = (-1,0,1,0)
dx = (0,1,0,-1)
from  math import factorial


def main():
    s = input()
    ans = 'Yes'
    for i in range(len(s)):
        if i%2 == 1:
            if s[i] != ' ':
                ans = 'No'
                break
        else:
            if ord(s[i]) < 97 or ord(s[i]) > 123:
                ans = 'No'
                break
    print(ans)
if __name__ == '__main__':
    main()