#include <stdio.h>

int main(int argc, const char **argv)
{
    int keylen, count, i;
    char buf[256];

    if (argc != 2) return 1;
    keylen = strlen(argv[1]);

    while ((count = fread(buf, 1, sizeof buf, stdin))) {
        for (i=0; i<count; i++) {
            buf[i] ^= argv[1][i % keylen];
        }
        fwrite(buf, 1, count, stdout);
    }

    return 0;
}