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

string gj(string a12,string b12) {
	int a11[2000],b11[2000],sum11[2000],alen1,blen1,slen1;
	string c="";
	memset(a11,0,2000);
	memset(b11,0,2000);
	memset(sum11,0,2000);
	alen1=a12.size();
	for(int i=0; i<alen1; i++) a11[i]=a12[alen1-(i+1)]-48;
	blen1=b12.size();
	slen1=max(alen1,blen1);
	for(int i=0; i<blen1; i++) b11[i]=b12[blen1-(i+1)]-48;
	for(int i=0; i<slen1; i++) {
		sum11[i]+=(a11[i]+b11[i]);
		if(sum11[i]>=10) sum11[i+1]++,sum11[i]-=10;
	}
	if(sum11[slen1]>0) slen1++;
	slen1--;
	for(int i=slen1; i>=0; i--) {
		c+=char(sum11[i]+int('0'));
	}
	return c;
}

int n;
string a[5005];
int main() {
	scanf("%d",&n);
	if(n==0) {
		printf("0");
		return 0;
	}
	a[0]="1",a[1]="1";
	for(int i=2; i<=n; i++) {
		a[i]=gj(a[i-1],a[i-2]);
	}
	cout<<a[n];
	return 0;
}

#2、10过不了

输入5000时返回乱码