#include <bits/stdc++.h>
#define ll long long
#define INF 1000000005
#define MOD 1000000007
#define EPS 1e-10
#define rep(i,n) for(int i=0;i<(int)(n);++i)
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;--i)
#define srep(i,s,t) for(int i=(int)(s);i<(int)(t);++i)
#define each(a,b) for(auto& (a): (b))
#define all(v) (v).begin(),(v).end()
#define len(v) (int)(v).size()
#define zip(v) sort(all(v)),v.erase(unique(all(v)),v.end())
#define cmx(x,y) x=max(x,y)
#define cmn(x,y) x=min(x,y)
#define fi first
#define se second
#define pb push_back
#define show(x) cout<<#x<<" = "<<(x)<<endl
#define spair(p) cout<<#p<<": "<<p.fi<<" "<<p.se<<endl
#define sar(a,n) cout<<#a<<":";rep(pachico,n)cout<<" "<<a[pachico];cout<<endl
#define svec(v) cout<<#v<<":";rep(pachico,v.size())cout<<" "<<v[pachico];cout<<endl
#define svecp(v) cout<<#v<<":";each(pachico,v)cout<<" {"<<pachico.first<<":"<<pachico.second<<"}";cout<<endl
#define sset(s) cout<<#s<<":";each(pachico,s)cout<<" "<<pachico;cout<<endl
#define smap(m) cout<<#m<<":";each(pachico,m)cout<<" {"<<pachico.first<<":"<<pachico.second<<"}";cout<<endl

using namespace std;

typedef pair<int,int> P;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<double> vd;
typedef vector<P> vp;
typedef vector<string> vs;

const int MAX_N = 200005;

#define getchar getchar_unlocked
#define putchar putchar_unlocked

inline int in() {
    int n = 0; short c;
    while ((c = getchar()) >= '0') n = n * 10 + c - '0';
    return n;
}

vector<int> vec[MAX_N];
int id[MAX_N];

int main()
{
    int n = in(), K = in(), T = in();
    rep(i,T){
        int l = in(),r = in();
        id[i] = in();
        vec[l-1].pb(T+i);
        vec[r].pb(i);
    }
    set<P> st = {P(-1,INF), P(T,INF)};
    int ans = 0, cnt = 0, sm = 0;
    rep(i,n){
        each(val,vec[i]){
            if(val >= T){
                cnt++;
                val -= T;
                auto it = st.lower_bound(P(val,INF));
                int nx = it->se;
                --it;
                int prv = it->se;
                if(nx-prv==1) sm--;
                if(nx == id[val]+1) sm++;
                if(prv == id[val]-1) sm++;
                st.insert(P(val,id[val]));
            }else{
                cnt--;
                auto it = st.lower_bound(P(val,INF));
                int nx = it->se;
                --it, --it;
                int prv = it->se;
                ++it, st.erase(it);
                if(nx-id[val]==1) sm--;
                if(id[val]-prv==1) sm--;
                if(nx-prv==1) sm++;
            }
        }
        if(cnt == K && sm == K-1) ans++;
    }
    cout << ans << "\n";
    return 0;
}
