上楼梯解答错误？！

#include <bits/stdc++.h> using namespace std;

int n; long long visited[80] = {0, 1, 2, 4};

long long dfs(int x) {

if(!visited[x])
	visited[x] = dfs(x-1)+dfs(x-2)+dfs(x-3);
return visited[x];

}

int main() {

while(cin>>n)
	cout << dfs(n) << '\n';
return 0;

}