#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#define ll long long
#define lll long long
#define ld long double
#define ull unsigned long long
#define ff first
#define ss second
#define pii pair<int,int>
#define pll pair<long long, long long>
#define vi vector<int>
#define vl vector<long long>
#define pb push_back
#define rep(i, b) for(int i = 0; i < (b); ++i)
#define rep2(i,a,b) for(int i = a; i <= (b); ++i)
#define rep3(i,a,b,c) for(int i = a; i <= (b); i+=c)
#define count_bits(x) __builtin_popcountll((x))
#define all(x) (x).begin(),(x).end()
#define siz(x) (int)(x).size()
#define forall(it,x) for(auto& it:(x))
using namespace __gnu_pbds;
using namespace std;
typedef tree<int, null_type, less<int>, rb_tree_tag,tree_order_statistics_node_update> ordered_set;
//mt19937 mt;void random_start(){mt.seed(chrono::time_point_cast<chrono::milliseconds>(chrono::high_resolution_clock::now()).time_since_epoch().count());}
//ll los(ll a, ll b) {return a + (mt() % (b-a+1));}
const ll INF_L = 1e18+40;
const ll MOD = 1e9+7;
struct seg
{
int l,r;
ll c;
bool operator<(const seg& other) const
{
return r < other.r;
}
};
lll INF = (lll)1e18;
pair<lll,int> dp[100001];
vector<seg> segs;
int n,m,K;
const int tree_siz = 1024*256-1;
pair<lll,int> min_[tree_siz+1];
ll oper[tree_siz+1];
void spych(int v)
{
min_[v*2].ff += oper[v];
min_[v*2+1].ff += oper[v];
oper[v*2] += oper[v];
oper[v*2+1] += oper[v];
oper[v] = 0;
}
pair<lll,int> get_min(int akt, int p1, int p2, int s1, int s2)
{
if(p2 < s1 || p1 > s2) return {INF,m};
if(p1 >= s1 && p2 <= s2) return min_[akt];
spych(akt);
return min(get_min(akt*2,p1,(p1+p2)/2,s1,s2),get_min(akt*2+1,(p1+p2)/2+1,p2,s1,s2));
}
void add_seg(int akt, int p1, int p2, int s1, int s2, ll x)
{
if(p2 < s1 || p1 > s2) return;
if(p1 >= s1 && p2 <= s2)
{
min_[akt].ff += x;
oper[akt] += x;
return;
}
spych(akt);
add_seg(akt*2,p1,(p1+p2)/2,s1,s2,x);
add_seg(akt*2+1,(p1+p2)/2+1,p2,s1,s2,x);
min_[akt] = min(min_[akt*2],min_[akt*2+1]);
}
void set_val(int akt, int p1, int p2, int p, pair<lll,int> x, int p3 = 0)
{
if(p1 == p2)
{
if(p3 == 1) min_[akt] = min(min_[akt],x);
else min_[akt] = x;
return;
}
spych(akt);
if(p <= (p1+p2)/2) set_val(akt*2,p1,(p1+p2)/2,p,x,p3);
else set_val(akt*2+1,(p1+p2)/2+1,p2,p,x,p3);
min_[akt] = min(min_[akt*2],min_[akt*2+1]);
}
pll solve(ll C)
{
rep(i,tree_siz+1)
{
min_[i] = {INF,m};
oper[i] = 0;
}
rep2(i,1,m) dp[i] = {INF,m};
dp[0] = {0,0};
set_val(1,0,tree_siz/2,0,{0,0});
vi to_add;
rep2(i,1,m)
{
bool is = 0;
if(segs[i].r != segs[i-1].r)
{
is = 1;
forall(it,to_add) add_seg(1,0,tree_siz/2,0,segs[it].l,segs[it].c);
to_add = {};
}
dp[i] = get_min(1,0,tree_siz/2,0,segs[i].l);
dp[i].ff += C;
dp[i].ss++;
set_val(1,0,tree_siz/2,segs[i].r,dp[i],!is);
to_add.pb(i);
}
pair<lll,int> ans = {INF,m};
vector<pll> pom;
rep2(i,1,m) pom.pb({segs[i].l,segs[i].c});
sort(all(pom));
ll c = 0;
int cur_pom = siz(pom)-1;
for(int i = m; i >= 1; i--)
{
while(cur_pom >= 0 && pom[cur_pom].ff >= segs[i].r) c += pom[cur_pom--].ss;
ans = min(ans,{dp[i].ff+c,dp[i].ss});
}
return {ans.ff-C*ans.ss,ans.ss};
}
int main()
{
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
//random_start();
cin >> n >> m >> K;
segs.resize(m+1);
segs[m] = {-1,-1,0};
rep(i,m) cin >> segs[i].l >> segs[i].r >> segs[i].c;
sort(all(segs));
ll l = 0;
ll r = 1e14;
ll res = 0;
while(l <= r)
{
ll C = (l+r)/2;
pll ans = solve(C);
if(ans.ss <= K)
{
res = ans.ff-C*(K-ans.ss);
r = C-1;
}
else l = C+1;
}
cout << res << "\n";
}
