import std;

alias fib = memoize !(fibImpl);
int fibImpl (int n) {
    if (n < 2) return n;
    return fib (n - 1) + fib (n - 2);
}

void main () {
    foreach (line; stdin.byLine) {
        auto n = line.to !(int);
        writeln (fib (n));
    }
}