#include <iostream>
#include <iomanip>
#include <cmath>
 
int main()
{
    long double pi = atan(1.)*4;
 
    int input;
    while(true)
    {
        std::cout << "Please enter how many digits of PI you would like to see (Max 20): ";
 
        if (!(std::cin >> input))
            return 255;
 
        if(input > 0 && input <= 20)
            break;
 
        std::cout << "That's not a valid number! Try again." << std::endl;
    }
 
    std::cout << std::setprecision(input);
    std::cout << "Pi approximated: " << pi << std::endl;
}
 

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