import math
import sys
 
def haversine(lat1, lon1, lat2, lon2):
     
    dLat = (lat2 - lat1) * math.pi / 180.0
    dLon = (lon2 - lon1) * math.pi / 180.0
 
    lat1 = (lat1) * math.pi / 180.0
    lat2 = (lat2) * math.pi / 180.0
 
    a = (pow(math.sin(dLat / 2), 2) +
         pow(math.sin(dLon / 2), 2) *
             math.cos(lat1) * math.cos(lat2));
    rad = 6371
    c = 2 * math.asin(math.sqrt(a))
    return round(rad * c)
 
if __name__ == "__main__":
    lat1 = float(sys.argv[1])
    lon1 = float(sys.argv[2])
    lat2 = float(sys.argv[3])
    lon2 = float(sys.argv[4])

    print(haversine(lat1, lon1, lat2, lon2))