代码如下``` #include<bits/stdc++.h> using namespace std;

int n, k, cnt; queue q[21];

int main(){ cin >> n >> k; for (int i=1; i<=n; i++){ string x; cin >> x; int s=x.size(); while (q[s-1].empty() == 0&&i-q[s-1].front()>k){ q[s-1].pop(); } cnt += q[s-1].size(); q[s-1].push(i); } cout << cnt; return 0; }