Lower Bound of a Confidence Interval

Every Ridgeline certificate records a measured average together with the margin of error for it — for the sensor you just worked through, 100 units and 3.92. Internally the lab keeps the two numbers apart, but the hospital's quality system will not accept a "plus or minus": its intake form has one field for the bottom of the accepted range and one for the top, and a certificate that does not fill both gets bounced back. The lab ships certificates for instruments on wildly different scales, so the conversion runs on whatever pair the calibration produced.

Task: Print the lower endpoint of the 95% confidence interval, rounded to 2 decimals. The conventions: the interval is symmetric about the measured average, because it was built from a two-sided normal critical value; the margin of error given is already the half-width for 95% confidence, so it is used exactly as it stands and is neither halved nor doubled; and rounding happens once, on the final value.

Input

The first line holds the measured average, a decimal number. The second line holds the margin of error, a non-negative decimal number on the same scale.

Output

One line holding the lower endpoint, rounded to 2 decimals and printed the way Python prints a float - 0.4, never 0.40.

Example:

Input:
100
3.92

Output:
96.08