#include
using namespace std;
int main() {
long int i, number, square = 0;
jump:
cout << "Input a natural number: ";</p>
cin >> number;
if (number <= 0) {</p>
cout << "Input error! Try again"<< endl;</p>
goto jump;
}
for(i = 1; i <= number; i++)</p>
square += i + i - 1;
cout << "The square of number " << number << " is " << square << endl;</p>
return 0;
}