#include <iostream>
#include <regex>
#include <numeric>

uint64_t stomac( const std::string &mac )
{
    static const std::regex r{ "([\\da-fA-F]{2})(:|$)" };

    auto it = std::sregex_iterator( mac.begin(), mac.end(), r );
    static const auto end = std::sregex_iterator();

    return std::accumulate( it, end, 0, []( uint64_t i, const std::sregex_iterator::value_type &v ) {
            return ( i << 8 ) + std::stol( v.str(1), nullptr, 16 );
    } );
}

int main()
{
    std::cout << std::hex << stomac( "00:00:12:24:36:4f" ) << std::endl;
}