/** from https://ru.stackoverflow.com/a/797911/23044 */
/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
        System.out.println(interleaved_sb("abc", "gfr"));
	}
    static String interleaved_sb(String a, String b)
    {
        assert a.length() == b.length();
        StringBuilder res = new StringBuilder();
 
        for(int i=0; i<a.length(); i++)
            {
                res.append(a[i]);
                res.append(b[i]);
            }
 
        return res.toString();
    }
}

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