How to make a F-curve with a constant and linear part?

As part of a problem I need to obtain a curve in the graph editor, that has a constant part , followed by a linear one.

for instance:

for the interval [0,100] the curve is y=0

for the interval [100,end] the curve is y=x-100

I tried under Add-Modifier>Generator, but the closest curve I found was only a y=mx+n curve. There is also the option of using python to shape the curve, but I do not know how. I assumed, that maybe it could be possible to draw the curve by hand, but it does not seem so.

How would you make a F-curve that looks like the white one in the picture ?

Simple driver expression frame if (frame > 100) else 0