What is the sum of the first 100 positive integers? The formula for
the sum of integers \(1\) through \(n\) is \(n(n+1)/2\). Define
\(n=100\) and then use R to compute the sum of \(1\) through \(100\)
using the formula. What is the sum?

### Example

With the code below you can compute the sum for the first 20 integers.
You can copy and past the code in the R console to evaluate that the code.

```
20*(20+1)/2
```

However, we can also define a variable n to re-use the formula for other values of n

- We first define the variable n and set it equal to 20
- Next we calculate the formula

```
n <- 20
n*(n+1)/2
```

We can reuse the same code and redefine n so to repeat the calculation for n=25.

```
n <- 25
n*(n+1)/2
```

### Exercise

Now, adjust the code from the example to calculate the sum of the first 100 integers.