#yuki894

def gcd(x,y):
 while y:
  x,y=y,x%y
 return x

def lcm(x,y):
 return x*y/gcd(x,y)

t,a,b=map(int,raw_input().split())
t-=1
print t/a+t/b+1-t/lcm(a,b)