#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<algorithm>
#include<queue>
#include<cmath>
#include<map>
using namespace std;
#pragma comment(linker, "/STACK:102400000,102400000")
#define ls i<<1
#define rs ls | 1
#define mid ((ll+rr)>>1)
#define pii pair<int,int>
#define MP make_pair
typedef long long LL;
typedef unsigned long long ULL;
const long long INF = 1e18+1LL;
const double pi = acos(-1.0);
const int N = 5e5+10, MM = 1e3+20,inf = 2e9;

const LL mod = 10000019ULL;
inline LL read()
{
    LL x=0,f=1;char ch=getchar();
    while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
    while(ch>=‘0‘&&ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();}
    return x*f;
}

map<ULL,int  > s;
ULL bhas[N],has[N],sqr[N];
int M,L;
char sa[N];
int vis[N];
int main() {
    sqr[0] = 1;
    for(int i = 1; i < N; ++i) sqr[i] = sqr[i-1] * mod;
    while(scanf("%d%d",&M,&L)!=EOF) {
        scanf("%s",sa+1);
        int n = strlen(sa+1);
        has[0] = 0;
        for(int i = 1; i <= n; ++i) {
            has[i] = has[i-1] * mod + sa[i] - ‘a‘ + 1;
        }
        int ans = 0;
        for(int i = 1; i <= L && i + M * L - 1 <= n; ++i) {
            int cnt = 0;
            s.clear();
            int ll = 1,rr = 0;
            for(int j = i; j + L - 1 <= n; j += L) {
                int l = j, r = j + L - 1;
                ULL now = has[r] - has[l-1]*sqr[L];
                if(s[now] == 0){
                    bhas[++rr] = now;
                    if(rr - ll + 1 >= M)ans+=1;
                    s[now] = 1;
                    continue;
                }
                else {
                    while(ll <= rr && bhas[ll]!=now) {
                        s[bhas[ll++]] = 0;
                    }
                    s[bhas[ll++]] = 0;
                    bhas[++rr] = now;
                    if(rr - ll + 1 >= M)ans+=1;
                    s[now] = 1;
                }
            }
        }
        printf("%d\n",ans);
    }
    return 0;
}