long int I = 0； //Declare and initialize I as a long integer.

term = 1.0/(I * I)； //For the constant 1.0, the C++ compiler will automatically convert it into a double type, and this division will automatically convert an int into a double during the operation. This is an implicit conversion and the compiler will complete it automatically.

If it is declared as long double I = 0；; //The result is the same, except that no type conversion is required.

You can keep asking me if you don't understand.