Simple Java, oneliner Ruby
Java recursion:\n\n    public String convertTo7(int num) {\n        if (num < 0)\n            return '-' + convertTo7(-num);\n        if (num < 7)\n            
**Java recursion:**\n\n    public String convertTo7(int num) {\n        if (num < 0)\n            return '-' + convertTo7(-num);\n        if (num < 7)\n            return num + "";\n        return convertTo7(num / 7) + num % 7;\n    }\n\n**Ruby oneliner:**\n\n```\ndef convert_to7(num)\n  num.to_s(7)\nend\n```
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