class Solution {
public:
    string frequencySort(string s) {
        map<char,int> m1;
        multimap<int,char> m2;
        map<char,int> :: iterator it;
        multimap<int,char>::iterator it1;
        string str = "";
        for(int i=0;i<s.length();++i)
         m1[s[i]]++;
        for(it=m1.begin();it!=m1.end();++it)
        m2.insert({it->second,it->first});
        for(it1=m2.begin();it1!=m2.end();++it1)
         {
            for(int j=it1->first;j>0;--j)
            {str.push_back(it1->second);}
         }
         reverse(str.begin(),str.end());
         return str;
     }
};