Peli

input/code.cpp: In function 'void set_io(std::__cxx11::string)':
input/code.cpp:19:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
         freopen((filename + ".in").c_str(), "r", stdin);
         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
input/code.cpp:20:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
         freopen((filename + ".out").c_str(), "w", stdout);
         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define all(x) (x).begin(), (x).end()
#define pb push_back
#define fi first
#define se second
#define sz size
#define rsz resize
#define ii pair<int,int>
#define vi vector<int>
#define vvi vector<vector<int>>

void set_io(string filename = "") {
    ios::sync_with_stdio(0);
    cin.tie(0);

    if (filename != "") {
        freopen((filename + ".in").c_str(), "r", stdin);
        freopen((filename + ".out").c_str(), "w", stdout);
    }
}

int N, K;
set<char> bag;

int main() {
	set_io("");

    cin >> N >> K;

    if (K < 3) {
        cout << 0 << endl;
        return 0;
    }

    string s; cin >> s;
    
    ll ans = 0;
    for (auto c : s) {
        if (bag.count(c) == 0) bag.insert(c);
        if (bag.sz() == 3) {
            bag = set<char>();
            ans++;
        }
    }

    cout << ans << endl;
}

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 2, 3

Verdict: WRONG ANSWER

Test 3

Group: 3

Verdict: WRONG ANSWER

Test 4

Group: 1, 2, 3

Verdict: ACCEPTED

Test 5

Group: 1, 2, 3

Verdict: ACCEPTED