// Slower C++ solution:
#include <bits/stdc++.h>

using namespace std;





#define li          long long int

#define rep(i,to)   for(li i=0;i<((li)(to));i++)

#define repp(i,start,to)    for(li i=(li)(start);i<((li)(to));i++)

#define pb          push_back

#define sz(v)       ((li)(v).size())

#define bgn(v)      ((v).begin())

#define eend(v)     ((v).end())

#define allof(v)    (v).begin(), (v).end()

#define dodp(v,n)       memset(v,(li)n,sizeof(v))

#define bit(n)      (1ll<<(li)(n))

#define mp(a,b)     make_pair(a,b)

#define rin rep(i,n)

#define EPS 1e-12

#define ETOL 1e-8

#define MOD 1000000007

typedef pair<li, li> PI;



#define INF bit(60)



#define DBGP 1





#define idp if(DBGP)

#define F first

#define S second

#define p2(a,b)     idp cout<<a<<"\t"<<b<<endl

#define p3(a,b,c)       idp cout<<a<<"\t"<<b<<"\t"<<c<<endl

#define p4(a,b,c,d)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<endl

#define p5(a,b,c,d,e)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<endl

#define p6(a,b,c,d,e,f)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<endl

#define p7(a,b,c,d,e,f,g)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<endl

#define p8(a,b,c,d,e,f,g,h)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<endl

#define p9(a,b,c,d,e,f,g,h,i)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<"\t"<<i<<endl

#define p10(a,b,c,d,e,f,g,h,i,j)        idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<"\t"<<i<<"\t"<<j<<endl

#define foreach(it,v)   for(__typeof((v).begin()) it=(v).begin(); it!=(v).end(); ++it)

#define p2p(x)      idp p2((x).F, (x).S)

#define dump(x,n)   idp{rep(i,n){cout<<x[i]<<" ";}puts("");}

#define dump2(x,n)  idp{rep(i,n){cout<<"["<<x[i].F<<" , "<<x[i].S<<"] ";}puts("");}

#define dumpi(x)    idp{foreach(it, x){cout<<(*it)<<" ";}puts("");}

#define dumpi2(x)   idp{foreach(it, x){cout<<"["<<(it)->F<<" , "<<(it)->S<<"] ";}puts("");}



#define read2d(a,w,h)   rep(i,h)rep(j,w)cin>>a[i][j]

#define dump2d(a,w,h)   rep(i,h){rep(j,w)cout<<a[i][j]<<" ";puts("");}



typedef pair<li, li> PI;



li h, w, n;

set<li> obj[200200];



int main() {

    cin >> h >> w >> n;

    rin{

        li x, y;

        cin >> x >> y;

        obj[x].insert(y);

    }



    li high = 1;

    repp(i, 1, h) {

        for (auto& y : obj[i + 1]) {

            if (y <= high) {

                cout << i << endl;

                return 0;

            }

        }

        if (high < w && obj[i + 1].count(high + 1) == 0) {

            high++;

        }

    }

    cout << h << endl;



    return 0;

}

// Faster C++ solution for the same problem (measured speedup: 4.629881964753027x):
#include <bits/stdc++.h>

using namespace std;





#define li          long long int

#define rep(i,to)   for(li i=0;i<((li)(to));i++)

#define repp(i,start,to)    for(li i=(li)(start);i<((li)(to));i++)

#define pb          push_back

#define sz(v)       ((li)(v).size())

#define bgn(v)      ((v).begin())

#define eend(v)     ((v).end())

#define allof(v)    (v).begin(), (v).end()

#define dodp(v,n)       memset(v,(li)n,sizeof(v))

#define bit(n)      (1ll<<(li)(n))

#define mp(a,b)     make_pair(a,b)

#define rin rep(i,n)

#define EPS 1e-12

#define ETOL 1e-8

#define MOD 1000000007

typedef pair<li, li> PI;



#define INF bit(60)



#define DBGP 1





#define idp if(DBGP)

#define F first

#define S second

#define p2(a,b)     idp cout<<a<<"\t"<<b<<endl

#define p3(a,b,c)       idp cout<<a<<"\t"<<b<<"\t"<<c<<endl

#define p4(a,b,c,d)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<endl

#define p5(a,b,c,d,e)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<endl

#define p6(a,b,c,d,e,f)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<endl

#define p7(a,b,c,d,e,f,g)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<endl

#define p8(a,b,c,d,e,f,g,h)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<endl

#define p9(a,b,c,d,e,f,g,h,i)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<"\t"<<i<<endl

#define p10(a,b,c,d,e,f,g,h,i,j)        idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<"\t"<<i<<"\t"<<j<<endl

#define foreach(it,v)   for(__typeof((v).begin()) it=(v).begin(); it!=(v).end(); ++it)

#define p2p(x)      idp p2((x).F, (x).S)

#define dump(x,n)   idp{rep(i,n){cout<<x[i]<<" ";}puts("");}

#define dump2(x,n)  idp{rep(i,n){cout<<"["<<x[i].F<<" , "<<x[i].S<<"] ";}puts("");}

#define dumpi(x)    idp{foreach(it, x){cout<<(*it)<<" ";}puts("");}

#define dumpi2(x)   idp{foreach(it, x){cout<<"["<<(it)->F<<" , "<<(it)->S<<"] ";}puts("");}



#define read2d(a,w,h)   rep(i,h)rep(j,w)cin>>a[i][j]

#define dump2d(a,w,h)   rep(i,h){rep(j,w)cout<<a[i][j]<<" ";puts("");}



typedef pair<li, li> PI;



li h, w, n;

li leftmost_obj[200200];



int main() {

    cin >> h >> w >> n;

    rep(i, 200200) {

        leftmost_obj[i] = INF;

    }

    rin{

        li x, y;

        cin >> x >> y;

        leftmost_obj[x] = min(leftmost_obj[x], y);

    }



    li high = 1;

    repp(i, 1, h) {

        if (leftmost_obj[i + 1] <= high) {

            cout << i << endl;

            return 0;

        }

        if (high < w && leftmost_obj[i + 1] > high + 1) {

            high++;

        }

    }

    cout << h << endl;



    return 0;

}