#include <bits/stdc++.h>
using namespace std;
long long dp[305][305];
long long cost[305][305];
int main() {
  for (int i = 0; i <= 300; i++)
    for (int j = 0; j <= 300; j++) dp[i][j] = cost[i][j] = 3000000000000;
  int n, m, k;
  cin >> n >> m >> k;
  for (int i = 0; i < m; i++) {
    long long l, r, c;
    cin >> l >> r >> c;
    for (int j = l; j <= r; j++) cost[l][j] = min(cost[l][j], c);
  }
  dp[0][0] = 0;
  for (int i = 1; i <= n; i++) {
    dp[i][0] = 0;
    for (int j = 1; j <= i; j++) {
      dp[i][j] = dp[i - 1][j];
      for (int k = 1; k <= i; k++)
        dp[i][j] =
            min(dp[i][j], dp[k - 1][max(0, j - (i - k + 1))] + cost[k][i]);
    }
  }
  if (dp[n][k] == 3000000000000)
    cout << -1 << endl;
  else
    cout << dp[n][k] << endl;
  return 0;
}
