C++ || Easy to Understand
\n map<int, int>m;\n    NumberContainers() {\n        \n    }\n    \n    void change(int index, int number) {\n        if(m.find(index) != m.end())\n           
```\n map<int, int>m;\n    NumberContainers() {\n        \n    }\n    \n    void change(int index, int number) {\n        if(m.find(index) != m.end())\n            m[index]=number;\n        else\n            m.insert({index,number});\n    }\n    \n    int find(int number) {\n        if(m.size() == 0)\n            return -1;\n        for(auto pr:m)\n        {\n            if(pr.second == number)\n                return pr.first;\n        }\n        return -1;\n    }\n```
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