Slow Sublime Text Output even with fast processor

I am using sublime text for contests. I have included these lines in my cpp file.
freopen("E:/codes/testcases/input.txt", "r", stdin); freopen("E:/codes/testcases/output.txt", "w", stdout);
but even a small file like outputing a+b takes 8 sec.
I am using i79750H processor.
I am unable to get which setting is wrong…