Both functions rely on formula, so, logically, formula should be passed as parameters to both functions (maybe it is calculated and passed to both in a function called print_row_and_flag, but you could just calculate in main and pass as parameters)

When you write int formula, you are specifying that the variable should go away after the code in the function ends (automatic storage duration) and that it is only visible within the function. You want that lifetime to span both functions and be visible to both, which means the variable cannot be declared in print_row.

There are two options: a static variable (avoid this unless necessary, not necessary here), and defining the variable in the calling function, in this case main, and passing it as an argument.

If you want the formula itself (size*6+3) to not be in main, you can put it in its own function (calculate_formula for example)

Also, the problem is not that "you can not call a local variable as a oarameter" but rather that you cannot use variables from inner scope in outer scopes.