// https://rosettacode.org/wiki/Fibonacci_sequence
import ballerina/io;
function fib_iter(int n) returns int {
    if (n < 2) {
        return n;
    }
    int fib_prev = 1;
    int fib = 1;
    int temp = 0;
    foreach int _ in int:range(2, n, 1) {
        temp = fib;
        fib  = fib_prev + fib;
        fib_prev = temp;
    }
    return fib;
}

public function main() {
    foreach int i in int:range(1, 21, 1) {
        io:println(fib_iter(i));
    }
}