There exists some function. There exists a function. You can just define the function this way as the area under the curve between some end point or the beginning of the interval and some x. If you define a function in that way, the derivative of this function is going to be equal to your continuous function. Or another way of saying it is that you always have an antiderivative, that any continuous function has an antiderivative. And so it's a couple of cool things. Any continuous function has an antiderivative.