/*
    第２種情報処理技術者試験    平成7年度・春期・午後 問7
                                BohYoh Shibata PREPARATION
*/

#include <stdio.h>
#include <string.h>

#define LLENG 60

char chtbl[] = { "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                 "abcdefghijklmnopqrstuvwxyz"
                 "0123456789,." };

main()
{
    FILE *ifp, *ofp;
    long psiz;
    int  p, s;
    char pch, tch, tbuf[LLENG+2];

    ifp = fopen("txt_file", "r");
    ofp = fopen("prg_file", "wb");
    fscanf(ifp, "%ld\n", &psiz);
    while ( psiz > 0 ) {
        fgets(tbuf, sizeof(tbuf), ifp);
        p = 0;
        while(p < LLENG && psiz > 0 ) {
            tch = strchr(chtbl, tbuf[p++]) - chtbl;
            pch = tch << 2;
            for (s = 4; s < 9 && psiz > 0 ; s += 2) {
                tch = strchr(chtbl, tbuf[p++]) - chtbl;
                pch |= tch >> (8 - s);
                fputc(pch, ofp);
                psiz--;
                pch = tch << s;
            }
        }
    }
    fclose(ifp);
    fclose(ofp);
}