The arc length is the product of the angle measure in radians and the radius.
... s = r·θ
So, the angle in radians is the ratio of arc length to radius.
... θ = s/r
To convert from radians to degrees, multiply by the conversion factor 180°/(π radians).
... y = s/r·(180°/π)
Then the angle is between
... 15/20·180/π ≈ 42.97
and
... 16/20·180/π ≈ 45.84
Suitable integers in this range are 43, 44, and 45.
One possible integer value of y is 44.