Class Year From E-Mail Address

Write a program that reads in a midshipman's e-mail
address and prints out his class year. For example,
if you read in m031220@usna.edu you would print out
"Class of 2003".  You may assume that the class year
is 2000 or later.
#include "si204.h"

int main() {
  // read alpha code
  char c = readchar(stdin); // read "m" character
  int alpha = readnum(stdin); // read number, we ignore the rest

  // compute class number
  int d, y;
  d = alpha / 10000;
  y = d + 2000;

  // write out result
  fputs("Class of ", stdout);
  writenum(y, stdout);
  fputs("\n", stdout);

  return 0;