Your physics professor is having a problem. He wants to see if his odometer is working properly. He has taken notes of traveling speeds and time traveled with that speed.

Question: Calculate and show the total distance traveled.

Input specification
You will be first given the number of input (n) where 0 ≤ n ≤ 5000. Then, in the following n lines, you will be given two integers:

• The time traveled (in minutes) where the time is between 1 and 400
• The speed (km per hour): an integer between 0 and 200

Output specification
Show a floating point number with two digits precision.

Explanation: The car has traveled for (120 minutes) two hours with 80 km per hour (traveled 160 kms). Then for 130 minutes, 40 km per hour, etc.