def f(n): s = 0 a,b = 1,2 _ = 2 if n == 1 or n == 2: s = n print(s) else: while True: if _ == n: print(s) break else: s = a + b a = b b = s _ += 1 n = int(input()) f(n)

#include<bits/stdc++.h> #define ll long long using namespace std; long long a[100005]; int main(){ long long n; cin >> n; a[1] = 1; a[2] = 2; for(int i = 3;i <= n;i++){ a[i] = a[i-1] + a[i-2]; } cout << a[n]; return 0; }

#include<bits/stdc++.h> using namespace std; int main(){ long long n,a[105]; a[0]=1; a[1]=1; cin >> n; for(long long i=2;i<=n;i++){ a[i]=a[i-1]+a[i-2]; } cout << a[n]; return 0; }