Convert String to size_t in C++

// C++ Program to declare a string variable without using stringstream.
#include <iostream>

using namespace std;

int main()
{
    string s1 = "Hello Geek";
    cout << s1 << endl;
    string s2;
    cin >> s2;
    cout << s2 << endl;

    return 0;
}

// C++ Program to convert the string to size_t using
// stringstream.
#include <iostream>
#include <stream>
#include <string>
using namespace std;

int main()
{
    string str = "246810";
    // breaking words
    stringstream stream(str);

    // associating a string object with a stream
    size_t output;

    // to read something from the stringstream object
    stream >> output;

    cout << output << endl;
    return 0;
}