+ محدودیت زمان: ۱ ثانیه + محدودیت حافظه: ۲۵۶ مگابایت ---------- Have you ever heard the phrase “Cosmic Twins”? The people who are born on the same day of the year, are called cosmic twins. he problem-setter thinks that the probability of existence of cosmic twins in group of $P$ people is relatively high, based on the number of cosmic twins found in SBU. Your task is to calculate this probability and verify his conjecture. # ورودی The input contains two space separated integers $P, D$ – the number of people and the number of days in a year respectively. $$1 \leq P, D \leq 400$$ # خروجی Print a number in a line indicating the probability of existence of at least one pair of cosmic twins in the group. The result should be printed with exactly 6 digits after decimal point. # مثال‌ها ## ورودی نمونه ۱ ``` 2 2 ``` ## خروجی نمونه ۱ ``` 0.500000 ``` ## ورودی نمونه ۲ ``` 22 365 ``` ## خروجی نمونه ۲ ``` 0.475695 ``` ## ورودی نمونه ۳ ``` 23 365 ``` ## خروجی نمونه ۳ ``` 0.507297 ```