#include <iostream>
using namespace std;

bool isNumber(char ch[])
{
    int i = 1;
    bool isNum;
    (ch[0] == '+' || ch[0] == '-' || (ch[0]>='0' && ch[0]<='9')) ?  isNum = true : isNum = false;
    while (ch[i]!=0)
    {

        (ch[i]>='0' && ch[i]<='9') ? isNum=isNum && true : isNum = isNum && false;
        ++i;
    }
    return isNum;
}

int main(int argc, char* argv[])
{
    if (argc>1)
        (isNumber(argv[1])) ? cout << "Number is entered" : cout << "It's not a number";
}