#include <iostream>
#include <vector>
using namespace std;

int main()
{
    vector<int> t;

    int cnt = 0;
    for ( ; ; cnt++) {
        int ten;
        cin >> ten;

        if (ten == 999)
            break;

        t.resize(cnt+1);
        t[cnt] = ten;
    }

    int sum = 0;
    for (int i=0; i<cnt; i++)
        sum += t[i];

    if (cnt != 0) {
        double avg = (double)sum / cnt;
        cout << avg << endl;
    }
    else
        cout << "No \'ten\'s in t." << endl;

    return 0;
}