Wake my up 2 14 var

#include "stdafx.h"
#include <iostream>
#include <math.h>
#include <string>
#include <vector>
#include <iomanip>

using namespace std;

string input = "";
int dotCount;

double read(string startMes, string strErr, string dotErr) { //Checks variable for correct input (fractional number)
    cout << startMes << ": ";
    getline(cin, input);
    dotCount = 0;
    bool onlyDigits = true;
    string dummy;
    while (!onlyDigits || (dotCount >= 0 && dotCount < 2)) { //Cycle for checking each char in input string
        for (int i = input.length() - 1; i >= 0; i--) {
            if (!isdigit(input[i])) {
                if (input[i] == '.') dotCount += 1; //Adds number if it counted dot. Reacts to wrong input with multiple dots
                else onlyDigits = false; //Changes bool if there is something except dots and digits
            }
        }
        if (onlyDigits && dotCount < 2) { //Checks if all requirements are met and return double variable from string
            return stod(input.c_str());
        }
        else { //Cycle if something is wrong, reseting all values and, saying what is wrong
            if (!onlyDigits) { cout << strErr << ", type again: "; }
            else if (dotCount > 1) { cout << dotErr << ", type again: "; }
            getline(cin, input);
            onlyDigits = true;
            dotCount = 0;
        }
    }
}


char readChar(string request) { //Function that reads char symbol for further input Y or N, also works with not capital letters
    do {
        string input = "";
        cout << request << ": ";
        getline(cin, input);

        if (input.length() == 1) return input[0]; //Check if user wrote more than 1 letter and asks him again
        else {
            cout << "Press Y or N" << endl;
        }
    } while (input.length() != 1);
}

unsigned long long int double_fact(int i) { //Function for calculating double factorial sum
    unsigned long long int factSum; factSum = 1;
    int j = 1;
    while (2 * j <= i + 1) {//Cycle for double factorial if factorial is doe
        if (i % 2 == 0) {
            factSum *= 2 * j;//Formula for even factorial
            ++j;
        }
        else { //Cycle if factorial is odd
            factSum *= (2 * j) - 1;//Formula for odd factorial
            ++j;
        }
    }
    return factSum;
}

int main() {
    cout << setprecision(10);//Sets the amount of integers that will be printed
    int n = 0;
    double x, alpha;
    long double sum, a_n, epsilon; sum = 0;
    do {do {//Do while cycle for main function, also do while cycle for x input
        x = read("Write X number, -1 < X > 1", "You wrote incorrect number with letters", "You wrote number with several dots");
    } while (!(x < 1) || !(x > -1));
    alpha = read("Write aplha number", "You wrote incorrect number with letters", "You wrote number with several dots");
    cout << setw(2) << "n" << setw(15) << "a_n" << setw(15) << "sum" << setw(15) << "epsilon" << endl;//Starts the table input
    if (dotCount == 0) {
        while (n <= alpha) { //Cycle for count a_n, sum and epsilon if alpha is integer
            a_n = double_fact(2 * n + 1)*pow(x, 2 * n) / double_fact(2 * n);
            sum += a_n;
            epsilon = (double_fact(2 * (n + 1) + 1)*pow(x, 2 * (n + 1)) / double_fact(2 * (n + 1))) / sum;
            cout << setw(2) << n << setw(15) << a_n << setw(15) << sum << setw(15) << epsilon << endl;
            n++;
        }
    }
    else {
        do {//Cycle for counting elements if alpha is fractional
            a_n = double_fact(2 * n + 1)*pow(x, 2 * n) / double_fact(2 * n);
            sum += a_n;
            epsilon = (double_fact(2 * (n + 1) + 1)*pow(x, 2 * (n + 1)) / double_fact(2 * (n + 1))) / sum;
            cout << setw(2) << n << setw(15) << a_n << setw(15) << sum << setw(15) << epsilon << endl;
            n++;
        } while (alpha < epsilon);
    }
    n = 0, sum = 0, epsilon = 0;
    }while (abs(readChar("Continue (Y/N)?") - 105) == 16);
    return 0;
}