simple solution , C++ , single  MAP
\nclass NumberContainers {\npublic:\n    map<int,int>m;\n    vector<pair<int,int>>vp;\n    \n    NumberContainers() {\n        \n    }\n    \n    void change(in
```\nclass NumberContainers {\npublic:\n    map<int,int>m;\n    vector<pair<int,int>>vp;\n    \n    NumberContainers() {\n        \n    }\n    \n    void change(int index, int number) {\n        \n        m[index]=number;\n        \n    }\n    \n    int find(int number) {\n        for(auto i:m)\n        {\n            if(i.second==number)\n            {\n                return i.first;\n            }\n        }\n        return -1;\n    }\n};\n\n/**\n * Your NumberContainers object will be instantiated and called as such:\n * NumberContainers* obj = new NumberContainers();\n * obj->change(index,number);\n * int param_2 = obj->find(number);\n */\n```
[]