Decimals have nothing to do with long integers. Long int means that it takes up more memory space than integer, so it can represent a larger number. Decimal is the counting method of this number.

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If only 158 is written without L, then in C/C++, the type of this number is int. If you bring the L after it, it means that the type of this number is long int, and the L after it has nothing to do with the size of this number itself. Only the number stored in C/C++ language as long int type is represented, and the size of the number itself is 158.

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There is something wrong with your thinking direction. Of course, the value of type int can be converted to type long int, but this conversion has nothing to do with your problem here.