n=int(input())
if n==1 :
    print(-1)
    exit()

t=str(n)
if int(t[0])!=1:
    print(-1)
    exit()

for i in range(1,len(t)):
    if int(t[i])==3:
        continue
    else:
        print(-1)
        exit()

print(len(t)-1)