import std.stdio, std.string, std.conv;

void main() {
    int n = readln.chomp.to!int;
    int[] fib = new int[n+1];
    fib[0] = fib[1] = 1;
    foreach (i; 2 .. n+1) {
        fib[i] = fib[i-1] + fib[i-2];
    }
    fib[n].writeln;
}
