#include <bits/stdc++.h>
using namespace std;
long long int n, m, k, dp[311][311], co[311][311];
int main() {
  for (int i = 0; i <= 308; i++)
    for (int j = 0; j <= 308; j++) co[i][j] = 1e15;
  scanf("%lld %lld %lld", &n, &m, &k);
  for (int i = 1; i <= m; i++) {
    long long int l, r, c;
    scanf("%lld %lld %lld", &l, &r, &c);
    for (int j = l; j <= r; j++) co[j][l] = min(co[j][l], c);
  }
  for (int i = 0; i <= 308; i++)
    for (int j = 0; j <= 308; j++) dp[i][j] = 1e15;
  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, k - (i - j + 1))] + co[i][k]);
      }
    }
  }
  cout << (dp[n][k] >= 1e15 ? -1 : dp[n][k]);
  return 0;
}
