/* package whatever; // don't place package name! */
import java.util.*;
import java.lang.*;
import java.io.*;
import java.util.regex.*;
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
{
final String label
= "23_fgh99@#"; System.
out.
println(label.
replaceAll("^[^a-zA-Z_]|(?<!^)[^a-zA-Z0-9_]",
"_"));
}
}
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