#include <bits/stdc++.h>
using namespace std;
long long a[301][301];
long long dp[301][301];
int main() {
  int n, m, k;
  cin >> n >> m >> k;
  for (int i = 1; i <= n; i++)
    for (int j = 1; j <= n; j++) a[i][j] = 1000000000ll * 50000ll;
  long long x, y, cost;
  for (int i = 1; i <= m; i++) {
    cin >> x >> y >> cost;
    a[x][y] = min(a[x][y], cost);
  }
  for (int i = 1; i <= n; i++)
    for (int j = i; j <= n; j++) {
      if (a[i][j] == 1000000000ll * 50000ll) continue;
      for (int k = i + 1; k <= j; k++) a[k][j] = min(a[k][j], a[i][j]);
    }
  for (int i = 1; i <= n; i++) {
    for (int j = 0; j <= n; j++) dp[i][j] = 1000000000ll * 50000ll;
    dp[i][0] = 0;
  }
  for (int i = n; i >= 1; i--) {
    for (int j = k; j >= 0; j--) {
      if (i + 1 <= n) dp[i][j] = min(dp[i][j], dp[i + 1][j]);
      for (int t = i; t <= n; t++) {
        dp[i][j] = min(
            dp[i][j], a[i][t] + (t + 1 <= n ? dp[t + 1][max(0, j - (t - i + 1))]
                                            : (j - (t - i + 1) == 0
                                                   ? 0
                                                   : 1000000000ll * 50000ll)));
      }
    }
  }
  if (dp[1][k] == 1000000000ll * 50000ll)
    cout << -1 << endl;
  else
    cout << dp[1][k] << endl;
  return 0;
}
