a = list(input())
b = set(a)

def start_1_3(l):
    if len(l)>1:
        if l[0]=='1' and l[1]=='3':
            return True
        else:
            return False
    else:
        return False
        
def count_3(l, s):
    if len(s) == 2:
        return len(l)-1
    else:
        return '-1'
        
if start_1_3(a):
    print(count_3(a, b))
else:
    print(-1)