#include <iostream>
#include <cstring>
#include <fstream>
using namespace std;
 
int strcnt(char big[16384], char small[16384])
{ char *p;
  int nr=0;
  p=strstr(big,small);
  while (p) 
  { nr++;
    p=strstr(p+1,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++)
        {       nr=0;
                for (j=0; j<=n-i; j++)
                {       strncpy(small,big+j,i);
                        nr=strcnt(big,small);
                        if (nr>=k && nr>reznr && rezl<i)
                        {       reznr=nr;
                                rezl=i;
                        }
                        
                }
        }
        g << rezl;
        f.close();
        g.close();
        return 0;
}