#include<cstdio>
using namespace std;
int n, i,j;
int a[200], b[200], c[200];
FILE * fin = fopen("nunta.in", "r");
FILE * fout = fopen("nunta.out", "w");
void adunare(){
	int m;
	if(a[0] > b[0]){
		m = a[0];
	}
	else{
		m = b[0];
	}
	int t = 0;
	for(int i = 1; i <= m; i++){
		c[i] = a[i] + b[i] + t;
		t = c[i] / 10;
		c[i] %= 10;
	}
	if(t != 0){
		c[++m] = t;
	}
	c[0] = m;
}
int main(){
	fscanf(fin, "%d", &n);
	if(n == 1){
		fprintf(fout, "1");
		return 0;
	}
	a[0] = a[1] = b[0] = b[1] = 1;
	for(i = 1; i < n; i++){
		adunare();
		for(j = 0; j <= b[0]; j++){
			a[j] = b[j];
		}
		for(j = 0; j <= c[0]; j++){
			b[j] = c[j];
		}
	}
	for(i = c[0]; i >= 1; i--){
		fprintf(fout, "%d", c[i]);
	}
	return 0;
}