#include <bits/stdc++.h>
using namespace std;
template <class T>
void chmax(T& a, const T& b) {
  a = max(a, b);
}
template <class T>
void chmin(T& a, const T& b) {
  a = min(a, b);
}
template <class T>
void uniq(T& c) {
  sort(c.begin(), c.end());
  c.erase(unique(c.begin(), c.end()), c.end());
}
template <class T>
string to_s(const T& a) {
  ostringstream os;
  os << a;
  return os.str();
}
template <class T>
T to_T(const string& s) {
  istringstream is(s);
  T res;
  is >> res;
  return res;
}
template <typename T>
void print_container(ostream& os, const T& c) {
  const char* _s = " ";
  if (!c.empty()) {
    __typeof__(c.begin()) last = --c.end();
    for (__typeof__((c).begin()) it = (c).begin(); it != (c).end(); ++it) {
      os << *it;
      if (it != last) cout << _s;
    }
  }
}
template <typename T>
ostream& operator<<(ostream& os, const vector<T>& c) {
  print_container(os, c);
  return os;
}
template <typename T>
ostream& operator<<(ostream& os, const set<T>& c) {
  print_container(os, c);
  return os;
}
template <typename T>
ostream& operator<<(ostream& os, const multiset<T>& c) {
  print_container(os, c);
  return os;
}
template <typename T>
ostream& operator<<(ostream& os, const deque<T>& c) {
  print_container(os, c);
  return os;
}
template <typename T, typename U>
ostream& operator<<(ostream& os, const map<T, U>& c) {
  print_container(os, c);
  return os;
}
template <typename T, typename U>
ostream& operator<<(ostream& os, const pair<T, U>& p) {
  os << "( " << p.first << ", " << p.second << " )";
  return os;
}
template <class T>
void print(T a, int n, const string& deli = " ", int br = 1) {
  for (int i = 0; i < n; ++i) {
    cout << a[i];
    if (i + 1 != n) cout << deli;
  }
  while (br--) cout << endl;
}
template <class T>
void print2d(T a, int w, int h, int width = -1, int br = 1) {
  for (int i = 0; i < h; ++i) {
    for (int j = 0; j < w; ++j) {
      if (width != -1) cout.width(width);
      cout << a[i][j] << ' ';
    }
    cout << endl;
  }
  while (br--) cout << endl;
}
template <class T>
void input(T& a, int n) {
  for (int i = 0; i < n; ++i) cin >> a[i];
}
template <class T>
void input(T* a, int n) {
  for (int i = 0; i < n; ++i) cin >> a[i];
}
void fix_pre(int n) {
  cout.setf(ios::fixed, ios::floatfield);
  cout.precision(10);
}
void fast_io() {
  cin.tie(0);
  ios::sync_with_stdio(false);
}
bool in_rect(int x, int y, int w, int h) {
  return 0 <= x && x < w && 0 <= y && y < h;
}
const int dx[] = {0, 1, 0, -1};
const int dy[] = {1, 0, -1, 0};
const double PI = acos(-1.0);
int main() {
  fast_io();
  const long long inf = ((long long)(1e15));
  int n, m, k;
  cin >> n >> m >> k;
  long long c[333][333];
  for (int i = 0; i < (int)(n); ++i)
    for (int j = 0; j <= (int)(n); ++j) c[i][j] = inf;
  for (int i = 0; i < (int)(m); ++i) {
    int l, r, _c;
    cin >> l >> r >> _c;
    --l, --r;
    for (int k = l; k <= r; ++k) chmin<long long>(c[l][k + 1], _c);
  }
  long long dp[333][333];
  for (int i = 0; i <= (int)(n); ++i)
    for (int j = 0; j <= (int)(n); ++j) dp[i][j] = inf;
  dp[0][0] = 0;
  for (int i = 0; i < (int)(n); ++i)
    for (int j = 0; j <= (int)(i); ++j) {
      chmin(dp[i + 1][j], dp[i][j]);
      for (int ni = i, nj = j; ni <= n; ++ni, ++nj)
        chmin(dp[ni][nj], dp[i][j] + c[i][ni]);
    }
  long long res = inf;
  for (int i = 0; i <= (int)(n); ++i)
    for (int j = k; j <= n; ++j) chmin(res, dp[i][j]);
  if (res == inf) res = -1;
  cout << res << endl;
}
