## Problem 2: Even Fibonacci numbers

*Difficulty: Easy

Problem

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.

How to solve:

First, we create a variable type int (or long) to store the total value, this variable is initialized by 2 (2 is the smallest even-valued term). And two numbers, for example, name n1 and n2 , initialized with 1 and 2, respectively. Moreover, we need a variable represent the Fibonacci value, you can name it whatever you want, I call it fibo (for short). We loop until fibo is still <= 4 millions , add n1 and n2 , assign that value to fibo, then we assign n2 to n1, and fibo to n2.
fibo = n1 + n2;

n1 = n2;

n2 = fibo;

And then see if fibo is an even number , if it is, add fibo to sum

sum += fibo;

Implementation (Java):

```public class Prob2 {

private static final intTHRESHOLD = 4000000;

public static void main(String[] args) {

int n1 = 1;

int n2 = 2;

int fibo = 0;

//2 is the smallest even-valued term

int sum = 2;

long cur = System.currentTimeMillis();

do {

fibo= n1+n2;

n1 = n2;

n2= fibo;

if(fibo % 2 == 0) {

sum+= fibo;

System.out.println(fibo);

}

}while(fibo <= THRESHOLD);

System.out.println(sum);

System.out.println("Took " + (System.currentTimeMillis()-cur) + "ms");

}

}
```

Solution took 0ms