s = input().strip()

n = len(s)
found = False

for i in range(n):
    for j in range(i+1, n):
        # Check if T is a valid main part
        valid_T = True
        C_odd = set()
        C_even = set()
        for k in range(i, j+1):
            pos_in_T = k - i
            if (pos_in_T + 1) % 2 == 1:
                # Must be a letter
                if s[k] == ' ':
                    valid_T = False
                    break
                C_odd.add(s[k])
            else:
                # Can be anything, collect if it's a letter
                if s[k] != ' ':
                    C_even.add(s[k])
        if not valid_T:
            continue
        if not C_odd.isdisjoint(C_even):
            continue
        
        # Check characters before i
        valid_before = True
        for k in range(i):
            if s[k] != ' ' and s[k] in C_odd:
                valid_before = False
                break
        if not valid_before:
            continue
        
        # Check characters after j
        valid_after = True
        for k in range(j+1, n):
            if s[k] != ' ' and s[k] in C_odd:
                valid_after = False
                break
        if not valid_after:
            continue
        
        # All conditions are satisfied
        found = True
        break
    if found:
        break

print("Yes" if found else "NO")