s=input().split() n=s[0] x=s[1] y=s[2] n=int(n) x=int(x) y=int(y) if n%x !=0: e=y//x+1 if n - e < 0: print(0) else: print(n-e) else: f=n - y//x if f < 0: print(0) else: print(f)