input: Write a python function to calculate the shortest path between two points in a 2D plane.
  assert shortestPath(10, 8, 15, 8) == 5
  assert shortestPath(0, 0, 3, 4) == 7
  assert shortestPath(-1, -2, 3, 2) == 8
output: def shortestPath(x1, y1, x2, y2):
      return int(((x2 - x1)**2 + (y2 - y1)**2)**0.5)