Maybe working lib

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

using namespace std;

string input = "";

int read_uint(const string start_mes) { //Checks variable for correct input (number)
    const string string_err = "You wrote letters in number";
    const string dot_err = "You wrote too many dots";
    const string neg_err = "You number is negative";
    const string repeat = ", type again: ";
    cout << start_mes << ": ";
    do { getline(cin, input); } while (input.length() == 0);
    int dot_count = 0;
    bool only_digits = true, negative = false;
    string dummy;
    while (!only_digits || dot_count == 0) {
        for (int i = input.length() - 1; i >= 0; i--) {
            if (!isdigit(input[i])) {
                if (input[i] == '.' || input[i] == ',') dot_count += 1;
                else if (input[i] == '-') negative = true;
                else only_digits = false;
            }
        }
        if (only_digits && dot_count == 0 && !negative) {
            return stoi(input.c_str(), NULL, 0);
        }
        else {
            if (!only_digits) { cout << string_err << repeat; }
            else if (dot_count != 0) { cout << dot_err << repeat; }
            else if (negative) { cout << neg_err << repeat; }
            getline(cin, input);
            only_digits = true;
            dot_count = 0;
            negative = false;
        }
    }
    return 0;
}

long long int read_int(const string start_mes) { //Checks variable for correct input (number)
    const string string_err = "You wrote letters in number";
    const string dot_err = "You wrote too many dots";
    const string neg_err = "You number is negative";
    const string repeat = ", type again: ";
    cout << start_mes << ": ";
    getline(cin, input);
    int dot_count = 0;
    bool only_digits = true, negative = false;
    string dummy;
    while (!only_digits || dot_count == 0) {
        for (int i = input.length() - 1; i >= 0; i--) {
            if (!isdigit(input[i])) {
                if (input[i] == '.' || input[i] == ',') dot_count += 1;
                else if (input[0] == '-') negative = true;
                else only_digits = false;
            }
        }
        if (only_digits && dot_count == 0) {
            return strtoll(input.c_str(), NULL, 0);
        }
        else {
            if (!only_digits) { cout << string_err << repeat; }
            else if (dot_count != 0) { cout << dot_err << repeat; }
            getline(cin, input);
            only_digits = true;
            dot_count = 0;
            negative = false;
        }
    }
    return 0;
}

char readChar(string request) {
    do {
        string input = "";
        cout << request << ": ";
        getline(cin, input);
        if (input.length() == 1) return input[0];
    } while (input.length() != 1);
    return 0;
}