func_code_string: #include <bits/stdc++.h>   using namespace std;   template <class c>   struct rge {     c b, e;   };   template <class c>   rge<c> range(c i, c j) {     return rge<c>{i, j};   }   template <class c>   auto dud(c *x) -> decltype(cerr << *x, 0);   template <class c>   char dud(...);   struct debug {     template <class c>     debug &operator<<(const c &) {       return *this;     }   };   long long __pow(long long x, long long y, long long M) {     long long res = 1;     while (y > 0) {       if (y & 1) res = (res * x) % M;       y >>= 1;       x = (x * x) % M;     }     return res % M;   }   long long __pow(long long x, long long y) {     long long res = 1;     while (y > 0) {       if (y & 1) res = (res * x);       y >>= 1;       x = (x * x);     }     return res;   }   long long mi(long long x, long long M) { return __pow(x, M - 2, M); }   long long gcd(long long a, long long b) {     if (b == 0) return a;     return gcd(b, a % b);   }   long long add(long long a, long long b, long long M) { return (a + b) % M; }   long long mul(long long a, long long b, long long M) { return (a * b) % M; }   long long sub(long long a, long long b, long long M) { return (a - b + M) % M; }   long long div(long long a, long long b, long long M) {     return (a * mi(b, M)) % M;   }   void umax(long long &a, long long b) { a = max(a, b); }   void umin(long long &a, long long b) { a = min(a, b); }   const long long N = 3e5 + 2, inf = 1e18, M = 998244353;   long long Test, n, m, k, query;   bool ok = 1;   void test_case() {     cin >> n >> k;     string s;     cin >> s;     s =  $  + s;     vector<long long> last(26);     vector<vector<long long>> dp(n + 1, vector<long long>(n + 1));     dp[0][0] = 1;     for (long long i = 1; i <= n; i++) {       dp[i][0] = 1;       for (long long j = 1; j <= n; j++) {         dp[i][j] = dp[i - 1][j - 1] + dp[i - 1][j];         if (last[s[i] -  a ]) dp[i][j] -= dp[last[s[i] -  a ] - 1][j - 1];       }       last[s[i] -  a ] = i;     }     long long ans = 0;     for (long long i = n; i >= 0 && k; i--) {       ans += min(k, dp[n][i]) * (n - i), k -= min(k, dp[n][i]);       debug() <<   [                <<  ans                    :                 << (ans)               <<  ]                      [                <<  k                    :                 << (k) <<  ]  ;     }     if (k)       cout << -1 << endl;     else       cout << ans << endl;   }   int32_t main() {     ios::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     Test = 1;     while (Test--) test_case();     return 0;   }   