uint256& uint256::SetCompact(uint32_t nCompact, bool *pfNegative, bool *pfOverflow)
{
    int nSize = nCompact >> 24;
    uint32_t nWord = nCompact & 0x007fffff;
    if (nSize <= 3) {
        nWord >>= 8*(3-nSize);
        *this = nWord;
    } else {
        *this = nWord;
        *this <<= 8*(nSize-3);
    }
    if (pfNegative)
        *pfNegative = nWord != 0 && (nCompact & 0x00800000) != 0;
    if (pfOverflow)
        *pfOverflow = nWord != 0 && ((nSize > 34) ||
                                     (nWord > 0xff && nSize > 33) ||
                                     (nWord > 0xffff && nSize > 32));
    return *this;
}

uint32_t uint256::GetCompact(bool fNegative) const
{
    int nSize = (bits() + 7) / 8;
    uint32_t nCompact = 0;
    if (nSize <= 3) {
        nCompact = GetLow64() << 8*(3-nSize);
    } else {
        uint256 bn = *this >> 8*(nSize-3);
        nCompact = bn.GetLow64();
    }
    // The 0x00800000 bit denotes the sign.
    // Thus, if it is already set, divide the mantissa by 256 and increase the exponent.
    if (nCompact & 0x00800000) {
        nCompact >>= 8;
        nSize++;
    }
    assert((nCompact & ~0x007fffff) == 0);
    assert(nSize < 256);
    nCompact |= nSize << 24;
    nCompact |= (fNegative && (nCompact & 0x007fffff) ? 0x00800000 : 0);
    return nCompact;
}

#!/bin/bash
echo "ibase=16;FFFF0000000000000000000000000000000000000000000000000000 / $1" | bc -l

$ ./target-to-difficulty.sh 000000000000000024DBE9000000000000000000000000000000000000000000
29829733124.04041574884510759883