//N阶楼梯上楼问题:一次可以走两阶或一阶,问有多少种上楼方式。(要求采用非递归)
#include <stdio.h>
#define max 100
int main() {
    int n, i;
    int dp[max];
    while (scanf("%d", &n) != EOF) {
        dp[1] = 1;
        dp[2] = 2;
        for (i = 3; i <= n; i++)
            dp[i] = dp[i - 1] + dp[i - 2];
        printf("%d", dp[n]);

    }
    return 0;
}