注意数据会很大，要用long long

#include<bits/stdc++.h>
using namespace std;

int main() {
	int n;
	vector<long long> arr(100);
	arr[0] = 0,arr[1]=1,arr[2]=2;
	for(int i=3;i<100;i++)
		arr[i] = arr[i-1]+arr[i-2];
	
	while(cin >> n)
		cout << arr[n] << endl;
}