#include <stdio.h>

int main()
{
    int x;
    extern int fib(int x);
    while (scanf("%d", &x) == 1)
        printf("%d\n", fib(x));
    return 0;
}


#define memosize 100
int fibmemo[memosize];  /* default init to 0 */


int fib(int x)
{
    if (x < 3) {
        return 1;
    } else if (x < memosize && fibmemo[x]) {
        return fibmemo[x];
    } else if (x < memosize) {
        fibmemo[x] = fib(x-1) + fib(x-2);
        return fibmemo[x];
    } else {
        return fib(x-1) + fib(x-2);
    }
}