#include <fstream>
using namespace std;

ifstream fin ("nunta.in" );
ofstream fout("nunta.out");

int N, M, i, j, K, ok, minim;

int a, b, c, n;

void CodeExpert(){
    fin >> n;
    if(n < 3){
        fout << 1;
        return;
    }
    else{
        a = 1; b = 1;
        for(i = 3; i <= n; i ++){
            c = a + b;
            a = b;
            b = c;
        }
        fout << c;
        return;
    }
    return;
}

int main(){
    CodeExpert();
    return 0;
}