Average of the First Two Valid Scores

Source: Phước Hưng OJ

Version: Phuoc Hung OJ Extended

Problem Statement

Read real-valued scores in order. Accept only scores in the inclusive interval $[0,10]$ and ignore all others. Take the first two accepted scores, compute their arithmetic mean, and print exactly two digits after the decimal point. The sequence ends at the second accepted score.

Input

Whitespace-separated real-valued scores with exactly two values in $[0,10]$, the last being the second valid score. Each number has at most two fractional digits.

Output

Print the arithmetic mean with two fractional digits, rounding a half-cent upward.

Subtasks

• Subtask 1 (20%): At most 5 scores, each of absolute value at most 10; exactly two accepted scores.
• Subtask 2 (30%): At most 100 scores, each of absolute value at most 1000; exactly two accepted scores.
• Subtask 3 (50%): At most 100001 scores, each of absolute value at most 1000000; exactly two accepted scores.

Examples

Example 1

Input

11.00 -1.50 7.00 9.00

Output

8.00

Explanation

11.00 and -1.50 are rejected. The first two accepted scores are 7 and 9; their mean is 8.00.

Example 2

Input

0 10

Output

5.00

Explanation

Both endpoints 0 and 10 are accepted. Their mean is 5.00.