import java.io.*;
class ComputeAverage{
	public static void main(String args[]) throws Exception{
		double total=computeTotal("MidtermMarksFile.txt");
		double numLines=countLines("MidtermMarksFile.txt");
		System.out.println(total/numLines);
	}
	public static int computeTotal(String fileName) throws Exception{
		FileReader fr=new FileReader(fileName);
		BufferedReader br=new BufferedReader(fr);

		int total=0;
		String line; 

		//Inv: line is the last line of text from fileName that was processed
		while(true){
			// read a line
			line=br.readLine(); 
			// if not null then convert to integer and add to total
			if(line!=null){
				int num=Integer.parseInt(line);
				total=total+num;
			} else {
				break;
			}
		}
		return(total);
	}

	public static int countLines(String fileName) throws Exception{
		FileReader fr=new FileReader(fileName);
		BufferedReader br=new BufferedReader(fr);

		int numLines=0;
		String line; 

		line=br.readLine(); // readLine returns null when file is exhausted
		//Inv: line is the next line of text from fileName TO BE PROCESSED
		while(line!=null && numLines<10){
			numLines=numLines+1;
			line=br.readLine(); 
		}
		if(line==null)return(numLines);
		while(line!=null){
			numLines=numLines+1;
			line=br.readLine(); 
		}
		return(numLines);
	}
}