#include <bits/stdc++.h>
using namespace std;
#define int long long
vector<pair<pair<int, int>, int>> vals;
vector<vector<pair<int, int>>> mem;
int N, M, K;
struct node {
int s, e, m, v, v1, lazy;
node* l, * r;
node(int _s, int _e) : s(_s), e(_e), m((_s + _e) / 2), v(1e15), v1(0), lazy(0) {
if (s != e)
l = new node(s, m),
r = new node(m + 1, e);
}
void prop() {
if (s == e || lazy == 0) return;
l->v += lazy;
r->v += lazy;
l->lazy += lazy;
r->lazy += lazy;
lazy = 0;
}
void reset() {
v = 1e15;
v1 = 0;
lazy = 0;
if (s == e) return;
l->reset();
r->reset();
}
void upd(int a, int b, int x) {
if (b < s || a > e) return;
if (a <= s && b >= e) {
v += x;
lazy += x;
return;
}
prop();
l->upd(a, b, x);
r->upd(a, b, x);
v = min(l->v, r->v);
if (l->v < r->v) v1 = l->v1;
else if (l->v > r->v) v1 = r->v1;
else v1 = min(l->v1, r->v1);
}
void upds(int n, int x, int o) {
if (s == e) {
if (x < v) {
v = x;
v1 = o;
}
return;
}
prop();
if (n <= m) l->upds(n, x, o);
else r->upds(n, x, o);
v = min(l->v, r->v);
if (l->v < r->v) v1 = l->v1;
else if (l->v > r->v) v1 = r->v1;
else v1 = min(l->v1, r->v1);
}
pair<int, int> qry(int a, int b) {
if (b < s || a > e) return { 1e15, 0 };
if (a <= s && b >= e) return { v, v1 };
prop();
auto resl = l->qry(a, b), resr = r->qry(a, b);
if (resl.first < resr.first) return resl;
if (resl.first > resr.first) return resr;
return { resl.first, min(resl.second, resr.second) };
}
} *root;
pair<int, int> relax(int lambda) {
root->reset();
root->upds(0, 0, 0);
vector<pair<int, int>> mem(M, { 0, 0 });
for (int i = 0; i < M; i++) {
mem[i] = root->qry(0, vals[i].first.second);
root->upd(0, vals[i].first.second, vals[i].second);
mem[i].first += lambda;
mem[i].first = max(mem[i].first, (int)-1e15);
mem[i].second++;
root->upds(vals[i].first.first, mem[i].first, mem[i].second);
}
return root->qry(0, N - 1);
}
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int a, b, c; cin >> N >> M >> K;
for (int i = 0; i < M; i++) {
cin >> a >> b >> c; a--, b--;
vals.push_back({ {b, a}, c });
}
sort(vals.begin(), vals.end());
root = new node(0, N - 1);
int low = 0, high = 1e15, ans = -1;
while (low <= high) {
int x = (low + high) / 2;
if (relax(x).second <= K) high = x - 1, ans = x;
else low = x + 1;
}
auto res = relax(ans);
cout << res.first - ans * K << '\n';
}
