Advice needed

[UnS3eN]

Just started learning C++ using Allain's "Jumping into C++". And I'm currently stuck on Chapter 4 Practice problem 1. I've actually done the thing and what is needed of me there, but I was just wondering about 1 thing. In the below code, then I build and run it, if I enter letters at the "person's age" prompt, the program just runs the rest of the code printing every 'cout' on the way. Is there any way to stop this behaviour?

#include <iostream>
#include <string>

int main()
{
    std::string name1 = "<unknown>";
    std::string name2 = "<unknown>";
    int age1;
    int age2;
// entering data
    std::cout << "What's the name of the first person?" << "\n";
    std::getline(std::cin, name1, '\n');

    std::cout << "What's the name of the second person?" << "\n";
    std::getline(std::cin, name2, '\n');

    std::cout << "Please enter " << name1 << "'s age:" << "\n";
    std::cin >> age1;

    std::cout << "Please enter " << name2 << "'s age:" << "\n";
    std::cin >> age2;


// checking if age != 0
    if (age1 == 0 ) {
        std::cout << "Age nas to be numeric and greater than 0. Please re-enter " << name1 << "'s age:"<< "\n";
        std::cin >> age1;
    }
    if (age2 == 0) {
        std::cout << "Age nas to be numeric and greater than 0. Please re-enter " << name2 << "'s age:"<< "\n";
        std::cin >> age2;
    }
// main task body
//checking if both are above 100
    if (age1 > 100 && age2 > 100) {
        std::cout << "Have they gone senile yet?";
    }
//checking if person 1 is older than 100
    else if (age1 > 100) {
        std::cout << name1 << " is one old fk!";
    }
//same for person 2
    else if (age2 > 100) {
        std::cout << name2 << " is one old fk!";
    }
// are they the same age?
    else if (age1 == age2) {
        std::cout << name1 << " and " << name2 << " are of the same age" << "\n";
    }
// is there only a year difference?
    else if (age1 - age2 == 1) {
        std::cout << name1 << " is older by a year." << "\n";
    }
    else if (age2 - age1 == 1) {
        std::cout << name2 << " is older by a year." << "\n";
    }
//main comparison
    else if (age1 > age2) {
        std::cout << name1 << " is older by " << age1 - age2 << " years." << "\n";
    }
    else if (age1 < age2) {
        std::cout << name2 << " is older by " << age2 - age1 << " years." << "\n";
    }

}

[vlad from moscow]

Stream std::cin can read data only when it is in a good state. If an error occured (you entered a letter instead of a number) the state of the stream is bad and it read nothing until you will clear the state.

[UnS3eN]

So I need to either implement some kind of error check or simply limit the usable input characters to numbers only, right?

[vlad from moscow]

You should check the state of the stream after each reading.

[UnS3eN]

Ok, thx. Will keep that in mind.