#include <iostream>
using namespace std;
char p[16000010];
const int prim=111111111;
int hash[prim];
int find(int v) {
    int a = v / 32;
    int b = v % 32;
    return (hash[a]&(1<<b));
}

void insert(int v) {
    int a = v / 32;
    int b = v % 32;
    hash[a] |= 1 << b;
}

int main()
{
	int length,num;
	cin>>length>>num;
	scanf("%s",p);
	int sum;
	int i;
	int j;
	int ans=0;
	for(i=0;i<=strlen(p)-length;i++)
	{
		sum=0;
		for(j=i;j<i+length;j++)
		{
			sum+=num*sum+p[j]-'a';
		}
		if(find(sum)==0)
		{
			ans++;
		}
		insert(sum);
	}
	cout<<ans<<endl;
	
	return 0;
}