#include <bits/stdc++.h>
using namespace std;
const long long inf = 1000000000000000000;
long long a[301][301];
long long b[301][301];
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie();
  cout.tie();
  for (long long i = 0; i <= 300; i++) {
    for (long long j = 0; j <= 300; j++) {
      a[i][j] = inf;
      b[i][j] = inf;
    }
  }
  long long n, m, k;
  cin >> n >> m >> k;
  while (m--) {
    long long l, r, c;
    cin >> l >> r >> c;
    a[l][r] = min(a[l][r], c);
  }
  for (long long i = 0; i <= n; i++) {
    for (long long j = 1; j <= n; j++) {
      a[j][i] = min(a[j][i], a[j - 1][i]);
    }
  }
  for (long long i = 0; i < n; i++) {
    b[i][0] = 0;
    for (long long j = 0; j <= i; j++) {
      if (b[i][j] == inf) continue;
      b[i + 1][j] = min(b[i + 1][j], b[i][j]);
      for (long long k = i + 1; k <= n; k++) {
        b[k][j + (k - i)] = min(b[k][j + (k - i)], b[i][j] + a[i + 1][k]);
      }
    }
  }
  long long res = inf;
  for (long long i = 0; i <= n; i++) {
    res = min(res, b[i][k]);
  }
  if (res == inf)
    cout << -1 << '\n';
  else
    cout << res << '\n';
  return 0;
}
