#include <iostream>

#define N 100

using namespace std;



int main() {

unsigned long long int f[N];

int n;

f[1]=1;

f[2]=2;

for (int i=3; i<N; i++){

f[i]=f[i-1]+f[i-2];

}

while (cin >> n){

cout << f[n] <<endl;

}

}