/* e289 */
/* AC (0.2s, 64.6MB) */
#pragma warning( disable : 4996 )
#include <iostream>
#include <string>
#include <unordered_map>
using namespace std;
unordered_map <string, long long> umap;
long long n, m, l = 0, r = 0, cata = 0, ans = 0;
string s[200001];
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
cin >> m >> n;
for (int i = 0; i < n && cin >> s[i]; ++i);
for (int i = 0; i < m; ++i)
{
if (!umap[s[i]])
++cata;
++umap[s[i]];
}
l = 0, r = m;
for (; r <= n;)
{
ans += (m == cata);
if (--umap[s[l]] == 0)
--cata;
if (umap[s[r]]++ == 0)
++cata;
++l, ++r;
}
cout << ans;
return 0;
}