Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:

```
1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
```

By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.

## Sample 00

## Sample 01

## input01.txt

```
4000000
```

## output01.txt

```
4613732
```

## Solution

`main.go`

```
package main
import (
"fmt"
)
func main() {
var (
n, r int
)
fmt.Scan(&n)
n1, n2, n3 := 1, 1, 2
for n3 < n {
r += n3
n1 = n2 + n3
n2 = n1 + n3
n3 = n1 + n2
}
fmt.Println(r)
}
```