#include <bits/stdc++.h>
using namespace std;
long long n, m, k;
long long dp[305][305], cost[305][305];
const long long inf = 1e18;
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cin >> n >> m >> k;
  fill(cost[0], cost[n + 1], inf);
  fill(dp[0], dp[n + 1], inf);
  for (long long i = 1; i <= m; i++) {
    long long l, r, c;
    cin >> l >> r >> c;
    cost[l][r] = min(cost[l][r], c);
  }
  dp[0][0] = 0;
  for (long long i = 1; i <= n; i++) {
    dp[i][0] = 0;
    for (long long j = 1; j <= i; j++) {
      dp[i][j] = min(dp[i][j], dp[i - 1][j]);
      long long mn = inf;
      for (long long l = 1; l <= j; l++) {
        mn = min(mn, dp[i - l][j - l]);
        if (cost[i - l + 1][i] == inf || mn == inf) continue;
        dp[i][j] = min(dp[i][j], mn + cost[i - l + 1][i]);
      }
    }
  }
  long long ans = inf;
  for (long long i = k; i <= n; i++) ans = min(ans, dp[n][i]);
  if (ans == inf) ans = -1;
  cout << ans << "\n";
  return 0;
}
