//#include <fstream>
#include <cstdio>
using namespace std;

//ifstream fin ("nunta.in" );
//ofstream fout("nunta.out");
FILE *fin = fopen("nunta.in", "r");
FILE *fout= fopen("nunta.out","w");

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

long long a, b, c, n;

void CodeExpert(){
    //fin >> n;
    fscanf(fin, "%d", &n);
    if(n < 2){
        fprintf(fout, "1");
        return;
    }
    else
    if(n == 2){
        fprintf(fout, "2");
        return;
    }
    else{
        a = 1; b = 1;
        for(i = 3; i <= n+1; i ++){
            c = a + b;
            a = b;
            b = c;
        }
        fprintf(fout, "%d", c);
        return;
    }
    return;
}

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