import math
a = list(map(int, input().split()))
n=a[0]
k4=a[1]
k2=a[2]

k=math.ceil(n/4)
kFloor=n//4
if k<=k4:
    print(k)
else:
    m=math.ceil((n-kFloor*4)/2)

    if m<=k2:
        print(k+m)
    else:
        print(-1)