I test my program a lot of times and the program pass all the test, but it still fails on Test#7, could somebody provide me with some additional test to check?

It will be great if the result of the test will be large number.

yes, big num will be needed

50 250
41409732703108026572448942476041207839411119408173570127621420289526490759097327483136

50 300
3660144008320861404705392514284143308670326732628084621145897204106027006076468826991924409

you can test the test case by printf("%d",1/0);