#include <bits/stdc++.h>
using namespace std;
long long cost[333][333];
long long dp[333][333];
int n, m, k;
int main() {
  cin.sync_with_stdio(false);
  cin >> n >> m >> k;
  for (int i = 0; i <= n; i++)
    for (int j = 0; j <= n; j++) dp[i][j] = cost[i][j] = 1e18;
  for (int i = 0; i < m; i++) {
    int left, right, cur;
    cin >> left >> right >> cur;
    for (int j = left; j <= right; j++) {
      for (int len = 1; len <= right - j + 1; len++) {
        cost[j][len] = min(cost[j][len], cur * 1ll);
      }
    }
  }
  dp[0][0] = 0;
  for (int i = 0; i < n; i++) {
    for (int j = 0; j <= i; j++) {
      if (dp[i][j] == 1e18) continue;
      dp[i + 1][j] = min(dp[i + 1][j], dp[i][j]);
      for (int k = i + 1; k <= n; k++) {
        dp[k][j + k - i] = min(dp[k][j + k - i], dp[i][j] + cost[i + 1][k - i]);
      }
    }
  }
  long long ans = 1e18;
  for (int i = k; i <= n; i++) {
    ans = min(ans, dp[n][i]);
  }
  if (ans == 1e18) ans = -1;
  cout << ans << endl;
  return 0;
}
