题解 | BFS

a=input()
ok=True
for i in range(len(a)-2):
    if (a[i]=="B" or a[i]=="b") and (a[i+1]=="o" or a[i+1]=="O") and (a[i+2]=="b" or a[i+2]=="B"):
        print(i)
        ok=False
        break
if ok==True:
    print("-1")