Maximum Number

Write a program that reads in positive integers from
the user, each separated by a space, and the whole
terminated by a negative number (e.g. 3 22 10 -2),
and returns the largest of the numbers entered (not
including the terminated negative number!).
#include "si204.h"

int main() {
  fputs("Enter numbers separated by spaces"
        " and ending with a negative.\n", stdout);

  // initialization
  int nextnum;
  int max;

  // read first number
  nextnum = readnum(stdin);
  // the first number is the max so far!
  max = nextnum;

  // Loop while the user enters more data
  while (nextnum >= 0) {
    // check whether nextnum is the biggest so far
    if (nextnum > max) {
      max = nextnum;

    // read the next value
    nextnum = readnum(stdin);

  // write out result
  fputs("The max is ", stdout);
  writenum(max, stdout);
  fputs("\n", stdout);

  return 0;