The person moves 12 km North and then 15 km South, resulting in a net displacement of 3 km South (15 km South - 12 km North). Simultaneously, the person moves 15 km East and then 19 km West, resulting in a net displacement of 4 km West (19 km West - 15 km East). The final position is 3 km South and 4 km West of the starting point. Using the Pythagorean theorem, the distance from the starting point is the square root of (3^2 + 4^2), which equals the square root of (9 + 16) or the square root of 25, resulting in 5 km.