Get the highest number of 'n' numbers

#include <iostream>
using namespace std;

double returnBiggest();

int main() {
    double biggest = returnBiggest();
    cout << "The biggest one is:" << biggest << endl;
    return 0;
}

double returnBiggest() {
    double aBiggest;
    double cValue;
    cout << "Please, insert first value: ";
    if (!(cin >> aBiggest)) {
        cout << "At least one value is needed" << endl;
        exit(1);
    }
    cout << endl;
    cout << "Please, insert value (insert any other character for finish program): ";
    while (cin >> cValue) {
        if (cValue > aBiggest)
            aBiggest = cValue;
        cout << endl;
        cout << "Please, insert value (insert any other character for finish program): ";
    }
    return aBiggest;
}