#include <iostream>
#include <cstring>
#include <fstream>
using namespace std;

int strcnt(char big[16384], char small[16384], int k)
{ char *p;
  int nr=0;
  p=strstr(big,small);
  while (p && nr<=k) 
  { 	nr++;
    	p=strstr(p+strlen(small),small);
  }
  return nr;
}

int main()
{
	char big[16384],small[16384];
	int n,k,i,j,nr,reznr=0,rezl=0;
	ifstream f("substr.in");
	ofstream g("substr.out");
	f >> n >> k >> big;
	for (i=2; i<=n/k; i++)
		for (j=0; j<=n-i; j++)
		{	strncpy(small,big+j,i);
			nr=strcnt(big,small,k);
			if (nr>=k && rezl<i)
			{	reznr=nr;
				rezl=i;
			}
			
		}
	g << rezl;
	f.close();
	g.close();
	return 0;
}