def circumference(pList):
    n=len(pList)
    lengde=0
    for i in range(0,n,2):
        x1=pList[i]
        y1=pList[i+1]
        x2=pList[(i+2)%n]
        y2=pList[(i+3)%n]
        lengde+=edgeLength(x1,y1,x2,y2)
    return lengde