- #include <iostream> 
- using namespace std; 
-   
- long long arr[61] = {0}; 
-   
- long long num_of_ways(int n){ 
- 	if(arr[n]) { 
- 		return arr[n]; 
- 	} 
- 	else { 
- 		arr[n] = num_of_ways(n-1) + num_of_ways(n-2) + num_of_ways(n-3); 
- 	} 
- 	return arr[n]; 
- } 
- int main() { 
- 	int n; 
- 	cin >> n; 
- 	arr[0] = 1; 
- 	arr[1] = 1; 
- 	arr[2] = 2; 
- 	cout << num_of_ways(n); 
- 	return 0; 
- } 
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