Plant Growth Rate Query

You are given a sequence of operations to record the height of a plant on specific days and to query its average growth rate over a period. There are two types of operations:

• record d h: Record that the plant's height is h on day d.
• query d1 d2: Query the average growth rate between day d1 and day d2.

For a query, if the heights on both days are recorded, the average growth rate is computed as $$\text{growth rate} = \frac{H(d_2)-H(d_1)}{d_2-d_1},$$ and the result is to be printed with exactly 4 decimal places. If either day does not have a recorded height, the output is 0.0000.

All input is read from standard input (stdin) and all output should be written to standard output (stdout).

inputFormat

The first line of input contains an integer n — the number of operations. The following n lines each contain an operation in one of the following two formats:

• record d h — record that on day d the plant's height is h.
• query d1 d2 — query the average growth rate between day d1 and day d2.

outputFormat

For every query operation, output a line containing the computed growth rate formatted to exactly 4 decimal places. If one or both of the specified days have no recorded height, output 0.0000 for that query.

6
record 1 3
record 2 8
record 3 10
record 4 15
record 5 18
query 2 5

3.3333