#include main () { auto char buf[128]; register int ch; register int packed; register char *scan; while (gets (buf)) { for (scan = buf; *scan != '\000'; ) { ch = *scan++; if (ch > '9') { packed = (ch - '7') << 4; } else { packed = (ch - '0') << 4; } ch = *scan++; if (ch > '9') { packed |= (ch - '7'); } else { packed |= (ch - '0'); } putchar (packed); } } }