/* 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 int count7(int n) 
    	{
    		return (7 > n) ? 0 : ( ( 7 == n % 10) ? 1 + count7(n / 10) : 0 + count7(n / 10));  
    	}
 
	public static void main (String[] args) throws java.lang.Exception
	{
		System.out.println(count7(717));
	}
}

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