C++ add 1+2+3+...+N - c++

Question

I've been having trouble with a problem from my C++ book. It wasn't required to do, but I want to get it to work:
Sum of numbers
Write a program that asks the users for a positive integer value and that uses a loop to validate the input.* The program should then use a second loop to compute the sum of all the integers from 1 up to the number entered. For example, if the user enters 50, the loop will find the sum of 1, 2, 3, 4, ... 50.
*I'm not asking for this first loop, just the second. But if you feel like coding it go ahead.
It's pretty simple to write a program that decreases a number until it reaches one:
#include <iostream>
using namespace std;
int main()
{
int number;
cout << "Enter a number: ";
cin >> number;
while(number >= 1)
{
cout << number << " ";
number--;
}
system("pause"); //I usually go with cin.get() but my current
//compiler doesn't handle it
return 0;
}
But if you to add "number - 1" to a number, the number becomes bigger and now number - 1 will increase from thereon. For example, 7 + 6 = 13, 13 + 12 = 25, 25 + 24 = 49, etc. Here's the program I am trying to adapt to make work:
#include <iostream>
using namespace std;
int main()
{
int number;
cout << "Enter a number: ";
cin >> number;
for(count = 1; count <= number; count++)
{
number += number - 1;
}
cout << "The sum is" << number << endl;
system("pause"); //
return 0;
}
This is an infinite loop, unfortunately.
Any ideas to how to adapt this program so it satisfies the question? Or links to source code that's already done it before, etc.
EDIT:
So this might be another issue entirely, but my code isn't compiling:
#include <iostream>
using namespace std;
int main()
{
int number, sum = 0;
cout << "Enter a number: ";
cin >> number;
for(count = 1; count <= number; count++)
{
number--;
sum += number;
}
cout << "The sum is" << sum << endl;
system("pause"); //
return 0;
}
EDIT 2: I just got rid of the for loop and changed it to "while(number >= 1)"

Answer 1

Something like this ?
int sum = number;
while (number-- > 0) {
sum += number;
}

Answer 2

I find a for loop neater, so I'll post an example for variety.
int n = Max Number
int sum = 0;
for(int i = 1; i <= n; i++) {
sum += i;
}
And for your compiling problem, unless I'm reading it wrong, you shouldn't be decrementing the number; it's defining what the max number is. Each loop you're incrementing the count, decrementing the number, then comparing them. I can't imagine that will give you anything meaningful. Erase the number--;, and it should work.