n,x,y = input().split() n = int(n) #total number of apples x = int(x) #eating apple speed y = int(y) #total hours #input #process eatenApples = y//x #the worm ate completed apples if y%x >0: eatenApples +=1 #the worm ate an incompleted apple leftApples = n - eatenApples #output if leftApples>=0: print( leftApples) else: print( 0)