cnt=0;c_check=0;w_check=0;ans=0
for i in input():
    if i=='c':
        cnt+=1
        c_check=1
    elif i=='w':
        if c_check==0:
            continue
        if w_check==0:
            w_check+=1
            cnt+=1
        else:
            cnt+=1
            w_check=0
            c_check=0
            ans+=cnt
            cnt=0
    elif c_check==1:
        cnt+=1
print(ans if ans else -1)