part1day1

//part1, day1 by @neon
#include <iostream>
#include <vector>
#include <sstream>
#include <fstream>

using namespace std;

int main(){
        ifstream input("./input.txt");
        string strline;
        long sum = 0;
        long num;
        while(!input.eof()){
                getline(input, strline);
                if(strline == "")continue;
                stringstream ss(strline);
                ss >> num;
                sum += num / 3 - 2;
        }
        cout << sum << endl;
}