#include <bits/stdc++.h>
using namespace std;
#define f(i,k,n) for(int i=k; i<n; i++)
#define ll long long
const int inf = INT_MAX;

void solve()
{
    int n,m,k;
    cin>>n>>m>>k;
    int x,y;
    int a[n+1][m+1]={0};
    f(i,0,k)
    {
        cin>>x>>y;
        a[x][y]++;
    }
    int c=0;
    int i=n;
    int j=m;
    int prev=0;
    int px,py;
    while(i>0 && j>0)
    {
        if(a[i][j]==1 && prev<j)
        {
            prev=j;
            c++;
            i--;
            j=m;
        }
        else if(j==1 && i>1)
        {
            i--;
            j=m;
        }
        else
        {
            j--;
        }
    }
    cout<<c;
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    int t=1;
    //cin>>t;
    while(t--)  solve();
    return 0;
}