typedef unsigned char uint8_t;

void wait(void) {
    volatile int i;
    for (i = 0; i < 30000; ++i) 
        /*empty*/;
}

int main(void) {
    void wait(void);
    uint8_t c1, c2, i;
    volatile uint8_t* ddrb = (uint8_t*)0x37;
    volatile uint8_t* portb = (uint8_t*)0x38;

    *ddrb = 0xFF;
    while (1) {
        c1 = 0x80;
        c2 = 0x01;
        for (i = 0; i < 4; i++) {
            wait();
            *portb = ~(c1 | c2);
            c1 >>= 1;
            c2 <<= 1;
        }
    }
    return 0;
}