I’m 5’7” and 104 kg
That depends on your goal and your unique biology but:
There are 3,500 calories in a pound of fat, so, if you want to lose a pound per week then you must produce an aggregate caloric deficit of 3,500 over seven days. If you burn an average of 2,000 calories per day (BMR + activity) and fast for five days in seven, then those five fasted days will produce a deficit of 10,000 calories. That means you can eat an additional 6,500 calories on the weekend (10,500 total) and still average a deficit of 3,500 calories for the week.
But bear in mind that the figures above are generalized - the actual figures depend on your body and goals - and they are very crude. Your metabolism is not so simple as (calories in) - (calories out), though that is the essential input.
Frankly, given the simplistic form of your question, I think you should read more about nutrition before adopting any such extreme diet.
Did you fasted before? If you try a long fast without training before, you are attempting to run a marathon without ever running before. Take it slow, study what is ketogenic state and how fasting gets you there.
Note: it’s not about your calories intake, it’s about what you eat and the size of each food intake.
Btw, if you fast for weigh lose, than if you do something slightly wrong, you might end up not being able to control your hunger and gaining more weight than before the fast