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

struct MovingAverage
{
    queue<double> que; // push inserts element at end
                       // pop removes first element
    size_t windowSize;
    double sum;

    MovingAverage(size_t size) { windowSize = size; }

    void add(double val)
    {
        sum += val;        
        que.push(val);
        if (que.size() > windowSize)
        {
            sum -= que.front();
            que.pop();
        }
    }

    double getAvg() { return que.size() == windowSize ? sum/windowSize : 0; }
};

int main(void)
{
    vector<double> testCase = { 1,2,3,4,5,6,7,8,9 };
    MovingAverage calc(3);
    for (auto i: testCase)
    {
        calc.add(i);
        cout << fixed << setprecision(1);        
        cout << "tick: " << i << " movingAvg: " << calc.getAvg() << endl;
    }
    return 0;
}