import sys
from collections import defaultdict

MOD = 998244353

def main():
    s = sys.stdin.readline().strip()
    n = len(s)
    
    dp_prev = defaultdict(int)
    
    # Initialize for the first character (i=0, 0-based)
    if s[0] == '?':
        for c in 'abcdefghijklmnopqrstuvwxyz':
            dp_prev[(None, c)] = 1
    else:
        dp_prev[(None, s[0])] = 1
    
    for i in range(1, n):
        dp_current = defaultdict(int)
        for (a_prev, b_prev), count in dp_prev.items():
            if s[i] == '?':
                possible_c = 'abcdefghijklmnopqrstuvwxyz'
            else:
                possible_c = [s[i]]
            
            for c in possible_c:
                if i == 1:  # Second character (i=1, 0-based)
                    if c == b_prev:
                        continue
                else:
                    if c == b_prev or c == a_prev:
                        continue
                
                new_state = (b_prev, c)
                dp_current[new_state] = (dp_current[new_state] + count) % MOD
        
        dp_prev = dp_current
        if not dp_prev:
            break
    
    result = sum(dp_prev.values()) % MOD
    print(result)

if __name__ == "__main__":
    main()