#include <stdio.h>

int main() {
   int n = 0;
   scanf("%d",&n);
   int arr[47];
   arr[0]=1;
   arr[1]=1;
   if (n == 1 || n == 2) {
        printf("1");
        return 0;
    }
   for(int i = 2;i<n;i++){
    
        arr[i]=arr[i-1]+arr[i-2];
    
   }
   printf("%d",arr[n-1]);
    return 0;
}