The obvious part. Calculate the result and get the mod. Use that as a response. But probably the result is such a big number that you will not be able to calcu

The obvious part. Calculate the result and get the mod. Use that as a response. But probably the result is such a big number that you will not be able to calculate. That is where you to look for a trick to only calculate the mod. May be ignoring significant numbers as you do the calculation.