Путанница

#include  <iostream>
#include  <cstdlib>
#include  <stdlib.h>
 
int main(int argc, char* argv[])
{
    setlocale (0,"");
    using namespace std;
    if (argc != 3 || !isdigit(atoi(argv[1])) && !isdigit(atoi(argv[2]))) 
{
    cerr << "Error\n";
    return EXIT_FAILURE;
}
        
    else /*(isdigit(atoi(argv[1])) && isdigit(atoi(argv[2])))*/
    {
    cout<<"sub= " <<((atoi(argv[1]))-(atoi(argv[2])))<<endl;
    cout<<"div= " <<((atoi(argv[1]))/(atoi(argv[2])))<<endl;
    cout<<"sum= " <<((atoi(argv[1]))+(atoi(argv[2])))<<endl;
    }
      
return 0;
}