Since floating-point numbers are to be output, the definition of variable Guo Jie should be floating-point Guo Jie =0, and the types should be consistent.

In the sentence Guo Jie += 1/fm, because 1 and fm are integers, the result of division is rounding, so it should be changed to.

Guo Jie += 1.0/fm, so you can get floating-point numbers.

You can keep asking questions.