function fib(fibs, time) {
    if(time === 0 || time === 1) return fibs[time] = 1;
    if(fibs[time]) return fibs[time];

    return fibs[time] = fib(fibs, time - 1) + fib(fibs, time - 2);
}

function main(_stdin){
    const stdin = _stdin.split('\n');
    const a = parseInt(stdin.shift(), 10);

   console.log(fib([1], a));
}


main(require('fs').readFileSync('/dev/stdin', 'utf8'));

