#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
int gcd(int A, int B) {
  if (!B) return A;
  return gcd(B, A % B);
}
long long int cost[301][301];
long long int dp[301][301];
int main() {
  int n, m, k;
  cin >> n >> m >> k;
  for (int i = 0; i <= n; i++)
    for (int j = 0; j <= n; j++) {
      cost[i][j] = (long long int)(1e18);
      dp[i][j] = (long long int)(1e18);
    }
  for (int i = 0; i < m; i++) {
    long long int a, b, c;
    cin >> a >> b >> c;
    for (int i = a; i <= b; i++) cost[a][i] = min(cost[a][i], c);
  }
  for (int i = 0; i <= n; i++) dp[i][0] = 0;
  for (int i = 1; i <= n; i++)
    for (int j = 0; j <= k; j++) {
      for (int l = 0; l < i; l++) dp[i][j] = min(dp[i][j], dp[l][j]);
      for (int l = 0; l <= j; l++)
        if (i - l - 1 >= 0 && j - l - 1 >= 0)
          dp[i][j] = min(dp[i][j], dp[i - l - 1][j - l - 1] + cost[i - l][i]);
    }
  if (dp[n][k] == (long long int)(1e18))
    cout << -1;
  else
    cout << dp[n][k];
}
