import sys
read=sys.stdin.buffer.read
readline=sys.stdin.buffer.readline
readlines=sys.stdin.buffer.readlines

d=int(readline())
h=list(map(int, read().split()))
INF=10**10
ans=INF
import itertools
for p in itertools.permutations(range(3)):
    if p[0]!=1 and p[2]!=1:
        continue
    x=h[:]
    if d==0:
        if x[p[0]]>x[p[1]] and x[p[1]]>x[p[2]]:
            print(0)
            exit()
        else:
            continue
    c1=max(0, (x[p[1]]-x[p[0]])//d+1)
    x[p[1]]-=c1*d
    if x[p[1]]<=0:
        continue
    c2=max(0, (x[p[2]]-x[p[1]])//d+1)
    x[p[2]]-=c2*d
    ans=min(ans, c1+c2)
if ans==INF:
    print(-1)
else:
    print(ans)