
Answer:
Following are the program in c++ Â language
#include <iostream> // header file
using namespace std; // namespace Â
int main() // main method
{
 int num, sum1 = 0; // variable declaration
 do
 {
   cout << "Enter the positive number:" << endl;
   cin >> num; // read number
   // cout << "You are entered a negative number" << endl;
 } while(num < 0);
 for(int k= 1; k <= num; k++)
   sum1 = sum1+k;
 cout << "Sum is: " << sum1<< endl;
 return 0;
}
Output :
Enter the positive number:5
Sum is: 15
Explanation:
In this program we taking a integer input in the "num" variable  from the user .
The do while loop is iterated  and check the entered integer validation i.e it check whether the entered integer is positive or not .If we entered the negative integer then it again ask for entering the value .
Finally we calculated the sum of all the integers from the 1 up to the user Entered value.