#include using namespace std; int kaijo(int x){ int result=1; while(x){ result *= x; x--; } return result; } int narabekata(int m,int n){ int result; result = kaijo(m+n)/(kaijo(m)*kaijo(n)); return result; } int main(){ int i; int N; int answer=0; scanf("%d", &N); for(i=0; i<=N/2; i++){ answer += narabekata(N-i*2,i); } printf("%d", answer); return 0; }