#include<bits/stdc++.h>
using namespace std;
int n;
string fib[60],a[60];
int main(){
	cin>>n;
    fib[1]="1";
    fib[2]="2";
    for(int i=3;i<=n;i++){
    	int num[10000],cnt=0;
    	for(int j=fib[n-1].length();j>=0;j--){
    		num[cnt]=fib[n-1][j]-'0'+fib[n-2][j]-'0';
    	    num[cnt+1]=num[cnt]/10;
    	    num[cnt]%=10;
    	    fib[i][j]=num[cnt++]+'0';
		}
		if(fib[i][0]=='0') {
			for(int j=0;j<fib[i].length()-1;j++)
			    fib[i][j]=fib[i][j+1];
		}
	} 
	for(int i=0;i<fib[n].length();i++)
	    cout<<fib[n][i];
    return 0;
}