#include <stdio.h>
#include <stdlib.h>

int main(void) {
    int N;
    long long C[60]; // case

    scanf("%d", &N);
    
    C[0] = 1; C[1] = 1;

    for (int i = 2; i <= N; i++) {
        C[i] = C[i-2] + C[i-1];
    }

/* 実はフィボナッチかよ !! */

    printf("%lld\n", C[N]);

    return EXIT_SUCCESS;
}