#include <bits/stdc++.h>
using namespace std;
long long dp[305][305], first[305][305];
int n, m, k;
int main() {
  scanf("%d%d%d", &n, &m, &k);
  long long inf = (long long)1e18;
  for (int i = 0; i <= n + 1; i++)
    for (int j = 0; j <= n + 1; j++) dp[i][j] = first[i][j] = inf;
  for (int i = 1; i <= m; i++) {
    int l, r, c;
    scanf("%d%d%d", &l, &r, &c);
    for (int x = l; x <= r; x++) first[l][x] = min(first[l][x], (long long)c);
  }
  dp[0][0] = 0;
  for (int i = 1; i <= n; i++)
    for (int j = 0; j <= i; j++) {
      dp[i][j] = dp[i - 1][j];
      for (int z = 1; z <= j; z++) {
        dp[i][j] = min(dp[i][j], dp[i - z][j - z] + first[i - z + 1][i]);
      }
    }
  long long ans = inf;
  for (int i = k; i <= n; i++) ans = min(ans, dp[n][i]);
  if (ans >= inf)
    puts("-1");
  else
    printf("%I64d\n", ans);
  return 0;
}
