Yes that will work, but prefer using const ierator. As const suggest (at least in recent compilers and libraries) also thread safe. So prefer :
std::multimap<int,std::string>::const_iterator it = dst.cbegin();
for(int count = 0;count<3 && it !=dst.cend();++it,++count)
std::cout<<it->second<<":"<<it->first<<std::endl;