#include <iostream>
#include <map>
using namespace std;
int main()
{
map<int,int> mymap={{1,0},{2,1},{9,2},{10,3},{11,4}};;
for(auto it=mymap.rbegin();it!=mymap.rend();){
int v=it->first;
++it;
mymap.erase(v);
}
std::cout << "done";
}
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