#include <bits/stdc++.h>
using namespace std;
 
int main()
{
    string g;
    int n, k;
    cin >> n >> k >> g;
 
    int maxi = -1;
 
    for (int i = 0; i <= n - 1; i++)
    {
        unordered_map<char, int> b; // In this map only distinct characters and distinct frequency is stored 
 
        for (int j = i; j <= n - 1; j++)
        {
            // Count the current character
            char number = g[j]; // g[j] means original input string store in number
            b[number] = b[number] + 1; // and increment it count the currrent character
 
            int l = j - i + 1;
 
            // Check exactly k distinct characters
            if (b.size() == k) // b.size will give us number key- value pairs stored in map // why we dont wrote b[i] it will only give the frequency of the character 
            {
                maxi = max(maxi, l);
            }
        }
    }
 
    cout << maxi << endl;
 
    return 0;
}

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

NwoyCmFhYmFhYWI=

7
2
aabaaab