题解 | 添加逗号
添加逗号
https://www.nowcoder.com/practice/f51c317e745649c0900996fd3f683aed
from os import name
n = input()
chang = len(n)
if chang % 3 == 0:
ci = chang // 3 - 1
else:
ci = chang // 3
for i in range(ci):
qu = (i * 4 + 3) * (-1)
cun = n[qu:]
n = n[:qu]
n = n + ','
n = n + cun
print(n)
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