[LintCode] Fibonacci

public int fibonacci(int n) {
        // write your code here
        int first = 0;
        if(n == 1)
            return first;
        int second = 1;
        if(n == 2)
            return second;
        int third = 0;
        for(int i = 3; i <=n; i++) {
            third = first+ second;
            first = second;
            second = third;
        }
        return third;
    }