/******************************************************************************
 *  Name:    Reference Solution
 *  NetID:   ref
 *  Precept: P00
 *
 *  Description:  Reads in integers from StdIn and outputs their average. 
 *                Stop reading either when the value 999 is input or when 
 *                there is no more input.
 ******************************************************************************/

public class Rainfall {
    public static void main(String[] args) {
        int    STOP  = 999;
        double total = 0.0;
        int    count = 0;
        
        // read from stdin
        while(!StdIn.isEmpty()) {
            // get the raindfall value
            int value = StdIn.readInt();
            
            // done if value == STOP value
            if (value == STOP)
                break;

            // remove negatives
            if (value < 0)
                value = 0;
        
            // update values
            total += value;
            count++;
        }
        
        // if no input, don't divide by 0
        if (count == 0)
            count = 1;
        
        // output solution
        StdOut.printf("%.2f", total/count);
    }
}