#include <bits/stdc++.h>
using namespace std;
const int N = 605;
const long long lim = 10000000000000000;
long long g[N][N], f[N][N];
int main() {
  ios_base::sync_with_stdio(false);
  int n, m, hehe;
  cin >> n >> m >> hehe;
  for (int i = 0; i <= n; ++i)
    for (int j = 0; j <= n; ++j) g[i][j] = f[i][j] = lim;
  for (int i = 0; i < m; ++i) {
    int x, y, z;
    cin >> x >> y >> z;
    for (int j = x; j <= y; ++j) g[j][y] = min(g[j][y], 1LL * z);
  }
  f[0][0] = 0;
  for (int i = 1; i <= n; ++i)
    for (int j = 0; j <= n; ++j) {
      f[i][j] = min(f[i][j], f[i - 1][j]);
      for (int k = 1; k <= i; ++k) {
        int t = j + i - k + 1;
        f[i][t] = min(f[i][t], f[k - 1][j] + g[k][i]);
      }
    }
  long long ans = lim;
  for (int i = hehe; i <= n; ++i) ans = min(ans, f[n][i]);
  if (ans == lim)
    cout << -1 << endl;
  else
    cout << ans << endl;
  return 0;
}
