#include <stdio.h>

int main(int argc, char *argv[]) {
  int n, n1, a, b, c;

  /*  Prints "n, (a,b)" where (a,b) is the n-th ordered pair of
      natural numbers under the following 
      enumeration of the ordered pairs of nat. numbers:

      <x,y> before <w,z>  iff  (x+y < w+z) or (x+y==w+z and x>w) */

  if (argc != 2) {
    printf("\n One argument--integer expected!  Exit.\n");
    return 1;
  }

  n = atoi(argv[1]);
  n1 = n;

  if (n == 0) {
    a = 0;
    b = 0;
  }
  else {
    c = 1;
    while (c <= n) {
      n = n - c;
      c ++;
    }  
    /* Now c-1 equals the # of executions of the loop's body;
       i.e., c-1 is the number of the diagonal that (a,b) is in. */
    a = c - n - 1;
    b = n;
    /* b is the offset of (a,b) in diagonal number c-1;
       a+b equals c-1. */
  }
  printf(" n = %d : (%d, %d)\n", n1, a, b);
 

  return 0;
}