#include <bits/stdc++.h>
using namespace std;

#define InTheNameOfGod cin.tie(0); ios::sync_with_stdio(0);

int main()
{
    InTheNameOfGod

    int sor, oszlop, pont;
    cin >> sor >> oszlop >> pont;

    vector<vector<int>> mezo(sor);

    for (size_t i = 0, a, b; i < pont; i++)
    {
        cin >> a >> b;
        mezo[a-1].push_back(b-1);
    }

    vector<int> vege(sor);
    for(int i = 0; i < sor; i++){
        sort(mezo[i].begin(), mezo[i].end());
        vege[i] = mezo[i].size()-1;
    }

    int robotok = 0;

    for(int i = 0; i < sor; i++)
    {
        int legtav = 0;
        int temp;
        if(vege[i] < 0) continue;
        robotok++;
        ////cout << "indit " << i << "\n";
        for(int j = i; j < sor; j++) {
            int ind = -1;
            int l, r, m;
            l = 0;
            r = vege[j];
            while(l <= r){
                m = (l+r) / 2;
                if(mezo[j][m] >= legtav){
                    r = m-1;
                    ind = m;
                }
                else{
                    l = m+1;
                }
            }

            ////cout << j << " " << (ind == -1 ? "semmi" : to_string(mezo[j][ind])) << " " << legtav << "\n";
            if(ind != -1){
                legtav = mezo[j][vege[j]];
                vege[j] = ind-1;
            }
        }
    }

    cout << robotok << "\n";
    
}