> 
无奈用将数据分段成两个I64..
后来在网上找了个ModPower的函数不会溢出.

I64 MultiMod(I64 &a, I64 b, I64 &c)
{
    I64 ret = 0, d = a;
    for (; b; b >>= 1, d <<= 1, d %= c)
        if ((b & 1))
            ret = (ret + d) % c;
    return ret;
}

I64 ModPower(I64 base, I64 exp, I64 &mod)
{
    I64 ret = 1;
    for (; exp; exp >>= 1, base = MultiMod(base, base, mod))
        if ((exp & 1))
            ret = MultiMod(ret, base, mod);
    return ret;
}

不过慢了点.375ms,用高精度才110ms