#include<cstdio>
using namespace std;
char v1[1001],v2[1001];
short n;
int main(){
    FILE *in = fopen ("nunta.in","r");
    FILE *out = fopen ("nunta.out","w");
    fscanf(in,"%hd",&n);
    v1[0] = 1; v2[0] = 1; v1[1] = 1; v2[1] = 1;
    for( int j = 2; j <= n; j ++ ){
        if( j%2 == 0 ){
            int t=0,i;
            for (i = 1; i <= v1[0] || t > 0; i ++ ){
                v1[i] +=  v2[i] + t;
                t = v1[i]/10;
                v1[i] %= 10;
            }
            v1[0] = i-1;
        }
        else{
            int t=0,i;
            for (i = 1; i <= v2[0] || t > 0; i ++ ){
                v2[i] +=  v1[i] + t;
                t = v2[i]/10;
                v2[i] %= 10;
            }
            v2[0] = i-1;
        }
    }
    short x;
    if( n % 2 == 0 ){
        for( int i = v1[0]; i >= 1; i -- ){
            x = v1[i];
            fprintf(out,"%hd",x);
        }
    }
    else{
        for( int i = v2[0]; i >= 1; i -- ){
            x = v2[i];
            fprintf(out,"%hd",x);
        }
    }
    return 0;
}