Competitions
PP2. Week 3: March 15 - 21
The angle between the vectors
Calculate the angle between two vectors.
Input data
Four integers x[1],y[1],x[2],y[2] - the coordinates of two nonzero vectors. All values do not exceed 10000 by the absolute value.
Output data
Print the value of an undirected angle between vectors with 5 decimal places in the interval [0; π].
Examples
Input example #1
2 1 3 5
Output example #1
0.56673