#include <cstdio>
#include <cstdlib>
#include <set>
#include <string>
#include <cstdlib>
#include <algorithm>
#include <cstring>
using namespace std;
int n, nc;
char data[16000007];
bool uniqueHashSet[16000007];
int randomIdx[256];
const long long MOD = 16000007;

int main() {
    int n, nc;
    scanf("%d %d\n", &n, &nc);
    scanf("%s", data);
    int dataLength = strlen(data);
    long long sum = 0, power = 1;
    int idx = 0, ans = 0;
    int BASE = nc;
    // 预处理 => 离散化
    for (int i = 0 ; i < dataLength; i ++) {
        if (randomIdx[data[i]] == 0) {
            randomIdx[data[i]] = ++idx;
        }
    }
    // 预处理 => 滚动hash power 值
    for (int i = 0; i < n - 1; ++i) {
        power = (power * BASE) % MOD;
    }


    // =>
    for (int i = 0; i < n; ++i) {
        int chRandomIdx = randomIdx[data[i]] - 1;
        sum = (sum * BASE + chRandomIdx) % MOD;
    }
    uniqueHashSet[sum] = true;
    ++ans;

    // => 滚动Hash计算 hash(s[i+1,i+N])= ( (hash(s[i,i+N−1]) − s[i] × Power(BASE, N − 1)) × BASE + s [i+N]) % M
    for(int i = n; i < dataLength; ++i) {
        int pewChRandomIdx = randomIdx[data[i-n]] - 1;
        sum = (sum - (pewChRandomIdx * power % MOD) + MOD) % MOD;

        int chRandomIdx = randomIdx[data[i]] - 1;
        sum = (sum * BASE + chRandomIdx) % MOD;
        if (!uniqueHashSet[sum]) {
            uniqueHashSet[sum] = true;
            ans ++;
        }
    }
    printf("%d\n", ans);
    return 0;
}