def convertToBase7(self, num):
if num == 0:
return "0"
s = []
minus = False
if num < 0:
num = num * (-1)
minus = True
while num > 0:
r = str(num % 7)
s.append(r)
num = num // 7
s = s[::-1]
if minus == False:
return "".join(d for d in s)
if minus == True:
n = "".join(d for d in s)
return "-" + n