You are given a sheet of paper with $100$ sentences, in the form of: There are exactly $x$ wrong sentences on this sheet.
There is exactly $1$ wrong sentence on this sheet.
There are exactly $2$ wrong sentences on this sheet.
...
There are exactly $99$ wrong sentences on this sheet.
There are exactly $100$ wrong sentences on this sheet.
Your task is find out which sentence says the truth (there can be only one).