Decompile the program with Ghidra, we learned that

* it return SUCCEED if result of function `r` is greater than 0, other wise FAILED.

Take a look at function `r`.

local_58 is using high frequencies [1209, 1336, 1477, 1633]
local_78 is using low frequencies [697, 770, 852, 941]

The big switch to check the state and the index of selected frequencies, `r` results in succeeded if the correct combination is found.

According to [keypad frequency](https://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling#Keypad)

DTMF keypad frequencies (with sound clips)
        1209 Hz    1336 Hz    1477 Hz    1633 Hz
697 Hz    1          2          3          A
770 Hz    4          5          6          B
852 Hz    7          8          9          C
941 Hz    *          0          #          D

```c
local_c = local_20 << 2 | local_c;
```

The lower two bits represent high frequency, the higher two bits represent low freqency.

Take a look at the switch block

```python
high = [1209, 1336, 1477, 1633]
low = [697, 770, 852, 941]

position 0: local_c should be 9(0b1001), (low[0b10],high[0b01]) = (852Hz,1336Hz) = 8
position 1: local_c should be 5(0b0101), (low[0b01],high[0b01]) = (770Hz,1336Hz) = 5
position 2: local_c should be 10(0b1010), (low[0b10],high[0b10]) = (852Hz,1477Hz) = 9
position 3: local_c should be 6(0b0110), (low[0b01],high[0b10]) = (770Hz,1477Hz) = 6
position 4: local_c should be 9(0b1001), (low[0b10],high[0b01]) = (852Hz,1336Hz) = 8
position 5: local_c should be 8(0b1000), (low[0b10],high[0b00]) = (852Hz,1209Hz) = 7
position 6: local_c should be 1(0b0001), (low[0b00],high[0b01]) = (697Hz,1336Hz) = 2
position 7: local_c should be 0xd(0b1101), (low[0b11],high[0b01]) = (941Hz,1336Hz) = 0
position 8: 0 is invalid, make it 1
```

So the key sequence is 859687201.
