We used [dnSpy](https://github.com/0xd4d/dnSpy) to decompile `Harekaze15Puzzle.exe`.
In `Form1` instance, `this.rnd` is a random number generator that was initialized with a seed.The seed is `-24110677` that was found by setting a breakpoint.
To get the flag, `this.rnd` have to generate a random number 1001 times.Perform `FlagGenerator.ShowFlag` with `this.rnd` shows the flag.
 ```this.rnd = new Random(-24110677);
for (int i = 0; i < 1001; i ++) {     this.rnd.Next(16); }
FlagGenerator.ShowFlag(this.rnd);```