text: #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <unistd.h>
  
  #define BUFSIZE 1000
  
  int
  main()
  {
  	char buffer[BUFSIZE];
  	char *c;
  
  	while (read(STDIN_FILENO, buffer, BUFSIZE) > 0) {
  		c = buffer;
  		while (*c && *c != '\n') {
  			switch (*c) {
  			case 'A':
  				putchar('A');
  				break;
  			case 'C':
  				putchar('C');
  				break;
  			case 'G':
  				putchar('G');
  				break;
  			case 'T':
  				putchar('U');
  				break;
  			default:
  				fprintf(stderr, "invalid char %c\n", *c);
  				return 1;
  			}
  			c++;
  		}
  	}
  	putchar('\n');
  	return 0;
  }
  