#include "bits/stdc++.h"
using namespace std;

const int maxN = 11;
int marks[11];
double grades[11];

void get_grade (int idx) {
	if (marks[idx] >= 80) {
		grades[idx] = 4.0;
	} else if (marks[idx] >= 70) {
		grades[idx] = 3.5;
	} else if (marks[idx] >= 60) {
		grades[idx] = 3.0;
	} else if (marks[idx] >= 50) {
		grades[idx] = 2.5;
	} else if (marks[idx] >= 40) {
		grades[idx] = 2.0;
	} else {
		grades[idx] = 0.0;
	}
}

int main () {
	 ios::sync_with_stdio(false);
	 cin.tie(nullptr);
	 cout.tie(nullptr);
	 for (int i = 1; i < maxN; ++i) marks[i] = rand() % 100 + 1;
	 //~ marks[1] = 100;
	 //~ marks[2] = 200;
	 for (int i = 1; i < maxN; ++i) {
		 get_grade(i);
	 }
	 double sum = 0;
	 for (int i = 1; i < maxN; ++i) {
		 sum += grades[i];
	 }
	 cout << sum / 10.0 << '\n';
}