S=list(input())
A=lambda B:[i for i, x in enumerate(S) if x == B]
C=A('c')
W=A('w')
O=200
for D in C:
 for i in range(len(W)-1):
  if D<W[i]:
   F=W[i+1]-D+1
   if O>F:O=F
if O==200:O=-1
print(O)