//int fib(int n);

int main() {
    int a = 4;
    int b = 5;
    while(a + b < 20)
        a++;
    return 0;
}

/*
int fib(int n) {
    if (n <= 1)
        return n;
    return fib(n - 1) + fib(n - 2);
}
*/