USING STRING (JAVA SOLN.)  ----- NOT USED BITS-----
Intuition\n Describe your first thoughts on how to solve this problem. \n\n# Approach\n Describe your approach to solving the problem. \n\n# Complexity\n- Time 
# Intuition\n<!-- Describe your first thoughts on how to solve this problem. -->\n\n# Approach\n<!-- Describe your approach to solving the problem. -->\n\n# Complexity\n- Time complexity:\n<!-- Add your time complexity here, e.g. $$O(n)$$ -->\n\n- Space complexity:\n<!-- Add your space complexity here, e.g. $$O(n)$$ -->\n\n# Code\n```\nclass Solution {\n    public int minChanges(int n, int k) {\n        \n        if(n==k)\n        return 0;\n        if(n<k)\n        return -1;\n        int c=0,i;\n        String str1=Integer.toString(n,2);\n        String str2=Integer.toString(k,2);\n        int k1=Math.max(str1.length(),str2.length());\n        int k2=Math.min(str1.length(),str2.length());\n        i=k1-k2;\n        int j=0;\n        for(int l=0;l<i;l++){\n           char ch=str1.charAt(l);\n           if(ch==\'1\')\n           c++;\n        }\n        for(;i<str1.length();i++){\n            char ch=str1.charAt(i);\n            char ch2=str2.charAt(j++);\n            if(ch==\'1\'&&ch2==\'0\')\n            c++;\n            else if(ch==\'0\'&&ch2==\'1\')\n            return -1;\n        }\n        return c;\n    }\n}\n```
['String', 'Java']