package test;
import java.util.Scanner;
public class Practice17 {
/**
* @param args
*/
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int sum = 0;
// System.out.println("輸入幾筆分數");
while (scanner.hasNext()) {
int a = scanner.nextInt();
// System.out.println("請輸入分數:");
for (int i = 1; i <= a; i++) {
int b = scanner.nextInt();
sum += b;
// System.out.println(sum);
}
double w = sum / a;
if (w >= 59) {
System.out.println("no");
} else
System.out.println("yes");
}
}
}