codeIQ_7の数を数える

import java.io.*;
class Main{

    public static void main(String[] args) throws IOException{
        int int7Cnt;
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));

        String strStdIn = in.readLine();

        while(strStdIn!=null){
            int7Cnt = 0;//カウンタ初期化
           int intMax = Integer.parseInt(strStdIn);

           for(int i=7;i<=intMax;i++){
               String strI = String.valueOf(i);
                for(int j=0;j<strI.length();j++){
                    if(strI.trim().substring(j,j+1).equals("7")){
                        int7Cnt++;
                    }
                }
           }
            System.out.println(int7Cnt);
            strStdIn = in.readLine();
        }
    }
}