#include <iostream>
#include <string>
using namespace std;
int main ()
{
    string str;
    cout <<"CONVERSION\n\n";
    cout <<"Base 11 to Decimal\n";
    cout << "Base 11: ";
    getline (std::cin,str);
 
    const auto bad_loc = str.find_first_not_of("0123456789aA");
    if(bad_loc != std::string::npos) {
    	cerr << "Invalid input\n";
        throw "bad input"; // or whatever handling
    }
 
    unsigned long ul = std::stoul (str,nullptr,11);
    cout << "Decimal: " << ul << '\n';
    return 0;
}

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