# Sum of n natural numbers in C++

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To get the sum of n numbers, there can be two cases:

- Add consecutive n numbers.
- Add any n numbers.

### Method 1 – Sum of n consecutive numbers without an array(using while loop)

**Algorithm:**

- Declare a variable
`n`

to store the number till which we need to find the sum. - Prompt the user to enter a value for
`n`

and store the input in`n`

. - Declare a variable
`sum`

and initialize it to 0 to store the sum of the numbers from 1 to`n`

. - Use a loop to iterate over the numbers from 1 to
`n`

, adding each number to`sum`

. - After the loop terminates, print the value of
`sum`

.

**Code:**

```
#include <iostream>
using namespace std;
int main()
{
int n, sum = 0;
cout << "Enter number till which you would like to add: ";
cin >> n;
while (n > 0)
{
sum += n;
n--;
}
cout << "\nSum is: " << sum << endl;
return 0;
}
```

**Output:**

```
Enter number till which you would like to add: 3
Sum is:6
```

### Method 2 – Sum of n numbers without an array(using while loop)

**Code:**

```
#include <iostream>
using namespace std;
int main()
{
int n, sum = 0, number;
cout << "How many numbers do you want to add? ";
cin >> n;
cout << "\nEnter numbers: ";
while (n > 0)
{
cin >> number;
sum += number;
n--;
}
cout << "\nSum is: " << sum << endl;
return 0;
}
```

**Output:**

```
How many numbers do you want to add? 7
Enter numbers:
1
2
3
4
5
89
34
Sum is:138
```

### Method 3: Sum of n numbers in array(using for loop)

**Code:**

```
#include <iostream>
using namespace std;
int main()
{
int n, sum = 0;
cout << "How many numbers do you want to add? ";
cin >> n;
int arr[n];
cout << "\nEnter numbers: ";
for (int i = 0; i < n; i++)
cin >> arr[i];
for (int i = 0; i < n; i++)
sum += arr[i];
cout << "\nSum is: " << sum << endl;
return 0;
}
```

**Output:**

```
How many numbers do you want to add? : 3
Enter numbers:
23
12
54
Sum is:89
```