import java.util.Scanner; import java.util.Collections; import java.util.ArrayList; import java.util.Arrays; import java.util.Queue; import java.util.ArrayDeque; import java.util.Deque; import java.util.PriorityQueue; import java.util.Set; import java.util.Map; import java.util.HashMap; import java.util.TreeSet; import java.util.Comparator; public class Main { static int mod = 1000000007; static int size = 510000; static long[] fac = new long[size]; static long[] finv = new long[size]; static long[] inv = new long[size]; //京都大学の過去問 public static void main(String[] args){ Scanner scanner = new Scanner(System.in); int n = scanner.nextInt(); long[] dp = new long[60]; dp[0] = 1; dp[1] = 1; for(int i = 2; i <= n+1; i++){ dp[i] = dp[i-1]+dp[i-2]; } System.out.println(dp[n]); } static class Edge{ int to; Edge(int to){ to = this.to; } } //繰り返し二乗法 public static long pow(long x, long n){ long ans = 1; while(n > 0){ if((n & 1) == 1){ ans = ans * x; ans %= mod; } x = x * x % mod; n >>= 1; } return ans; } //fac, inv, finvテーブルの初期化、これ使う場合はinitComb()で初期化必要 public static void initComb(){ fac[0] = finv[0] = inv[0] = fac[1] = finv[1] = inv[1] = 1; for (int i = 2; i < size; ++i) { fac[i] = fac[i - 1] * i % mod; inv[i] = mod - (mod / i) * inv[(int) (mod % i)] % mod; finv[i] = finv[i - 1] * inv[i] % mod; } } //nCk % mod public static long comb(int n, int k){ return fac[n] * finv[k] % mod * finv[n - k] % mod; } //n! % mod public static long fact(int n){ return fac[n]; } //(n!)^-1 with % mod public static long finv(int n){ return finv[n]; } static class Pair implements Comparable{ int x, y; Pair(int a, int b){ x = a; y = b; } @Override public boolean equals(Object o){ if (this == o) return true; if (!(o instanceof Pair)) return false; Pair p = (Pair) o; return x == p.x && y == p.y; } @Override public int compareTo(Pair p){ //return x == p.x ? y - p.y : x - p.x; //xで昇順にソート //return (x == p.x ? y - p.y : x - p.x) * -1; //xで降順にソート //return y == p.y ? x - p.x : y - p.y;//yで昇順にソート return (y == p.y ? x - p.x : y - p.y)*-1;//yで降順にソート } } static class UnionFind { int[] parent; public UnionFind(int size) { parent = new int[size]; Arrays.fill(parent, -1); } public boolean unite(int x, int y) { x = root(x); y = root(y); if (x != y) { if (parent[y] < parent[x]) { int tmp = y; y = x; x = tmp; } parent[x] += parent[y]; parent[y] = x; return true; } return false; } public boolean same(int x, int y) { return root(x) == root(y); } public int root(int x) { return parent[x] < 0 ? x : (parent[x] = root(parent[x])); } public int size(int x) { return -parent[root(x)]; } } public static int upperBound(long[] a,long val){ return upperBound(a,0,a.length,val); } public static int upperBound(long[] a,int l,int r,long val){ if(r-l==1){ if(a[l]>val) return l; return r; } int mid=(l+r)/2; if(a[mid]>val){ return upperBound(a,l,mid,val); }else{ return upperBound(a,mid,r,val); } } public static int lowerBound(long[] a,long val){ return lowerBound(a,0,a.length,val); } public static int lowerBound(long[] a,int l,int r,long val){ if(r-l==1){ if(a[l]