#include <iostream>
#include <string>
#include <cmath>
#include <algorithm>
#include <cstdio>
#include <iomanip>
using namespace std;
string A[500000]; 
int main()
{ 
	int n,k,i,j,cnt = 0;
	cin >> n >> k;
	for(i = 1;i <= n;i++)
	{
		cin >> A[i];
	}
	for(i = 1;i <= n;i++)
	{
		for(j = 1;j <= k;j++)
		{
			if(A[i + j].size() == A[i].size())
			{
				cnt++;
			}
		}
	}
	cout << cnt;
	return 0;
}