import sys
input = sys.stdin.readline

N, K = map(int, input().split())
G = [[] for i in range(N)]
for i in range(N):
    u, v = map(int, input().split())
    u, v = u - 1, v - 1
    G[u].append(v)
    G[v].append(u)
    
from collections import *
Q = deque([0])
dist = [-1] * N
par = [-1] * N
loop = -1
dist[0] = 0
while Q and loop == -1:
    u = Q.popleft()
    for v in G[u]:
        if v == par[u]:
            continue
        if dist[v] != -1:
            loop = dist[u] + dist[v] + 1
            break
        par[v] = u
        dist[v] = dist[u] + 1
        Q.append(v)
        
pre0, pre1 = K, 0
mod = 998244353
for _ in range(loop - 2):
    dp0 = pre1
    dp1 = pre0 * (K - 1) + pre1 * (K - 2)
    pre0 = dp0 % mod
    pre1 = dp1 % mod    

ans = pre0 * pow(K - 1, N - loop + 1, mod) + pre1 * (K - 2) * pow(K - 1, N - loop, mod)
print(ans%mod)