const rl = require("readline").createInterface({ input: process.stdin });
var iter = rl[Symbol.asyncIterator]();
const readline = async () => (await iter.next()).value;
void async function () {
// Write your code here
const n = parseInt(await readline());
let arr = new Array(n);
arr[0] = 1;
arr[1] = 1;
for(let i = 2; i < n; i++){
arr[i] = arr[i-1] + arr[i -2];
}
console.log(arr[n-1])
}()

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