import java.math.BigDecimal;
import java.util.Scanner;

import javax.swing.plaf.basic.BasicArrowButton;

public class Main {

    public static void main(String[] args) {
        Scanner inScanner = new Scanner(System.in);
        while(inScanner.hasNext()) {
            String string = inScanner.next();
            String string2 = inScanner.next();
            string = string.toLowerCase();
            string2 = string2.toLowerCase();
            char c = string.charAt(0);
            int number = 0;
            BigDecimal bigDecimal = BigDecimal.valueOf(0);
            for(int i = 0;i<string2.length();i++) {
                if(string2.charAt(i) == c) {
                    number ++;
                }
            }
            double number1 = number/1.0;  //int和double的转换。
            double d = number1/string2.length();
            bigDecimal = bigDecimal.add(BigDecimal.valueOf(d).setScale(5,BigDecimal.ROUND_HALF_UP)); //保留5位小数。
            System.out.println(bigDecimal);
        }
    }

}