[c] How to printf long long

  • Your scanf() statement needs to use %lld too.
  • Your loop does not have a terminating condition.
  • There are far too many parentheses and far too few spaces in the expression

    pi += pow(-1.0, e) / (2.0*e + 1.0);
    
  • You add one on the first iteration of the loop, and thereafter zero to the value of 'pi'; this does not change the value much.
  • You should use an explicit return type of int for main().
  • On the whole, it is best to specify int main(void) when it ignores its arguments, though that is less of a categorical statement than the rest.
  • I dislike the explicit licence granted in C99 to omit the return from the end of main() and don't use it myself; I write return 0; to be explicit.

I think the whole algorithm is dubious when written using long long; the data type probably should be more like long double (with %Lf for the scanf() format, and maybe %19.16Lf for the printf() formats.