//* Fail-safe reading with range checking *
#include <iostream>
using namespace std;

double ReadDouble(double min, double max) {
    double a;
    
    for (;;) {
        cin >> a;
        if ( cin.fail() ) {
            cin.clear();
            cin.ignore(256, '\n');
            cout << "I can't read it!\nplease reenter the number ";
        } else {
            if (a>=min && a<=max) break;
            else cout << "It's out of range!\nplease reenter the number ";
        }
    }
    return(a);
}

int main() {
    double x ;
    cout << "Please enter a decimal numbers between 0 and 4." << endl;
    cout << "x=";
    x=ReadDouble(0, 4);
    cout << "You have entered: " << "x=" << x << ", thank you." << endl;
    return(0);
}