def gcd(a,b):
    if b==0 :
        return a
    return gcd(b,a%b)

a = list(map(int, input().split()))
a[0] = a[0]-1
g = gcd(a[1],a[2])
l = a[2]*a[1]/g
ans = a[0]/a[1] + a[0]/a[2] - a[0]/l
ans = ans+1
print(ans)