def check(X):
    for i in range(len(X)):
        if X[i]!=X[len(X)-1-i]:
            return False
    return True
    
S=input()

if check(S)==True:
    X=S[:len(S)//2]+S[len(S)//2]+S[len(S)//2:]

    if check(X)==True:
        print(X)
    else:
        print("NA")

else:
    for i in range(len(S)):
        if S[i]!=S[len(S)-1-i]:
            X=S[:i]+S[len(S)-1-i]+S[i:]
            #print(X)

            if check(X)==True:
                print(X)
                exit()

            X=S[:len(S)-1-i+1]+S[i]+S[len(S)-1-i+1:]
            #print(X)

            if check(X)==True:
                print(X)
                exit()

            print("NA")
            exit()