S = list(input())
A = ["c","h","i","w","a","w","a"]
Al = 0
ans = 0
for i in range(len(S)):
    if S[i] == A[Al]:
        if Al <= 6:
            A[Al] = i
        if Al < 6:
            Al += 1
if type(A[-1]) == int:
    print(A[-1]-A[0])
else:
    print("-1")