The Accuracy Score

Harborline's sorting centre runs a screening model over every parcel that passes through. A human opens each parcel afterwards, so the team ends up with two labels per parcel: what it really contained, and what the model said. Monday's review always opens with the bluntest question there is — how often was the model simply right?

Task: Print the share of parcels whose two labels agree.

Input

The first line holds an integer n, the number of parcels (1 to 1000). Each of the next n lines holds two values separated by a single space: the true label first, the model's label second. Both are 1 (banned item inside) or 0 (clean).

Output

One line: a number between 0 and 1 with exactly two digits after the decimal point. A flawless week prints 1.00, not 1.

Example:

Input:
4
1 1
0 0
1 0
0 0

Output:
0.75