/* EASTER.C    An Easter Datecalculating program for Orthodox Easter.
               C code by melody@compulink.gr  -   Modifications
               by gj489@po.cwru.edu You may distribute the source as is  */

#include <stdio.h>
main(int argc,char **argv)
   {
   int year,a1,a2,a3,b1,b2,d,z;
   if(argc == 2)
     { year=atoi(argv[1]); goto just_do_it; }
   enter_year:
   printf("Enter year : ");
   scanf("%d",&year);
   just_do_it:
   if (year <= 0)
      {
      printf("Illigal year. Use years > 0");
      goto enter_year;
      }
   a1=year-(year/19)*19;
   a1=a1*19+16;
   a2=year-(year/4)*4;
   a2=a2*2;
   a3=year-(year/7)*7;
   a2=a2+4*a3;
   b1=a1-(a1/30)*30;
   a2=a2+6*b1;
   b2=a2-(a2/7)*7;
   d=3+b1+b2;
   printf("Orthodox Easter day for %d is on ",year);
   if (d <= 30)
      {
      printf("April %d\n",d);

      }
   else
      {
      printf("May %d\n",d-30);
      z=d-30;
      }
  }