In times of kites, being noon, Juan raised a kite and let out 'a' meters of string, and the kite string was at 'x' meters above the ground; if in the course of 5 minutes Juan releases another 'b' meters and the kite string is a 'y' meters from the ground, over what horizontal distance (d) did the kite fly in those five minutes?

Input

The input is composed of 4 numbers, namely:

• 'a' in meters representing the initial length of the string.
• 'x' in meters representing the height of the kite achieved with the initial length of the string.
• 'b' in meters, this is the extra length of string released in 5 minutes elapsed.
• 'y' in meters is the height of the kite relative to the floor after releasing the 'b' meters of string.

Output

The output is the distance 'd' covered horizontally by the kite in 5 minutes.

Example

Input:
10
5
5
10

Output:
2.52