| 시간 제한 | 메모리 제한 | 제출 | 정답 | 맞힌 사람 | 정답 비율 |
|---|---|---|---|---|---|
| 3 초 (추가 시간 없음) | 1024 MB | 105 | 49 | 40 | 43.956% |
One cold and foggy night, you walk down a shady alley. There should be a lamp every few metres but none of them seem to work, and in this night, not even the moon enlightens your path. Alone and in the dark, you wonder: "Even if there was a working lamp somewhere, how much would it lighten my way?". Now, back at home, you want to calculate this.
The alley can be modelled as a line with a length of $n$ metres. The fog has a uniform density and reduces the light of a lamp by a factor of 1ドル-p$ every metre. The brightness at one point is the sum of the light that reaches this point from every lamp. You want to calculate this brightness at some points after placing some lamps.
The input consists of:
+ b x" given two integers $b$ and $x$ (1ドル\leq b \leq 10^9$ and 1ドル\leq x \leq n$), place a lamp with brightness $b$ at position $x$.- b x" given integers $b$ and $x$ (1ドル\leq b \leq 10^9$ and 1ドル\leq x \leq n$), remove a lamp with brightness $b$ at position $x$. It is guaranteed that a lamp with that brightness was placed there earlier.? x" given one integer $x$ (1ドル\leq x \leq n$), calculate the brightness at position $x$.It can be shown that the brightness can be calculated as a fraction $\frac{P}{Q}$ where $Q$ is not divisible by 10ドル^9+7$. For each query of type "?", print the brightness as $P\cdot Q^{-1} \bmod 10^9+7$ in a single line.
5 6 0.25 + 4 2 ? 1 ? 2 ? 3 ? 4 ? 5
3 4 3 250000004 187500003
The brightness in the alley after placing the lamp will look like this:
5 7 0.33 + 9 1 ? 5 + 4 3 ? 2 ? 5 - 9 1 ? 2
312342734 470000012 341542736 760000008