C++ std::multiset返回值 has no member named ‘first’

error: ‘std::multiset::iterator {aka struct std::_Rb_tree_const_iterator}’ has no member named ‘first’  

multiset返回的直接是迭代器，所以没有first

// INTEGER EXAMPLE 
// CPP program to illustrate 
// Implementation of emplace() function 
#include  
#include  
using namespace std; 
  
int main() 
{ 
    multiset mymultiset{}; 
    auto result = mymultiset.emplace(3); 
    cout