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

int DP[100];

int fib(int n){
    if(n<=1)
        return n;

    if(DP[n] != -1)
        return DP[n];

    DP[n] = fib(n-1) + fib(n-2);

    return DP[n];
}

int main() {
    int n;
    scanf("%d", &n);

    for (int i=0; i<100; i++)
        DP[i] = -1;

    DP[0] = 0;
    DP[1] = 1;

    printf("%d\n", fib(n));
    
    return 0;
}