#include <algorithm>
#include <cassert>
#include <cfloat>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <deque>
#include <iostream>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <vector>
 
#define FOR(i,k,n) for (int (i)=(k); (i)<(n); ++(i))
#define rep(i,n) FOR(i,0,n)
#define all(v) begin(v), end(v)
#define debug(x) std::cerr<< #x <<": "<<x<<"\n"
#define debug2(x,y) std::cerr<< #x <<": "<< x <<", "<< #y <<": "<< y <<"\n"
 
typedef long long ll;
typedef std::pair<int, int> pii;
typedef std::vector<int> vi;
typedef std::vector<std::vector<int> > vvi;
typedef std::vector<ll> vll;
typedef std::vector<std::vector<ll> > vvll;
typedef std::deque<bool> db;
template<class T> using vv=std::vector<std::vector< T > >;

// cout vector
template<typename T> std::ostream& operator<<(std::ostream& s, const std::vector<T>& v) {
  int len=v.size();s<<"\n";rep(i,len){s<<v[i];if(i<len-1){s << "\t";}}s<<"\n";return s; }
// cout 2-dimentional vector
template<typename T> std::ostream& operator<<(std::ostream& s, const std::vector<std::vector<T> >& vv) {
  int len=vv.size();rep(i,len){s<<vv[i];} return s; }
// cout deque
template<typename T> std::ostream& operator<<(std::ostream& s, const std::deque<T>& v) {
  int len=v.size();s<<"\n";rep(i,len){s<<v[i];if(i<len-1){s << "\t";}}s<<"\n";return s; }
// cout 2-dimentional deque
template<typename T> std::ostream& operator<<(std::ostream& s, const std::deque<std::deque<T> >& vv) {
  int len=vv.size();rep(i,len){s<<vv[i];} return s; }
// cout set<cout-able>
template<typename T> std::ostream& operator<<(std::ostream& s, const std::set<T>& v) {
  s<<"\n";for(auto elm : v){s<<elm<<"\t";}s<<"\n";return s; }

inline void scan(int&a){scanf("%d",&a);}
inline void scan(int&a,int&b){scanf("%d%d",&a,&b);}
inline void scan(int&a,int&b,int&c){scanf("%d%d%d",&a,&b,&c);}
inline void scan(int&a,int&b,int&c,int&d){scanf("%d%d%d%d",&a,&b,&c,&d);}
inline void scan(std::vector<int>&v){int sz=v.size();rep(i,sz){scan(v[i]);}}
inline void scan(std::vector<std::vector<int> >&v){int sz=v.size();rep(i,sz){scan(v[i]);}}
inline void scan(ll&a){scanf("%lld",&a);}
inline void scan(ll&a,ll&b){scanf("%lld%lld",&a,&b);}
inline void scan(ll&a,ll&b,ll&c){scanf("%lld%lld%lld",&a,&b,&c);}
inline void scan(ll&a,ll&b,ll&c,ll&d){scanf("%lld%lld%lld%lld",&a,&b,&c,&d);}
inline void scan(std::vector<ll>&v){int sz=v.size();rep(i,sz){scan(v[i]);}}
inline void scan(std::vector<std::vector<ll> >&v){int sz=v.size();rep(i,sz){scan(v[i]);}}
inline void scan(char&a){scanf(" %c",&a);}
inline void scan(std::vector<char>&v){int sz=v.size();rep(i,sz){scan(v[i]);}}
inline void scan(std::vector<std::vector<char> >&v){int sz=v.size();rep(i,sz){scan(v[i]);}}
inline void scan(std::string&s){char BUF[3000000];scanf(" %s",BUF);s=std::string(BUF);}

inline void print(int a){printf("%d\n",a);}
inline void print(int a,int b){printf("%d %d\n",a,b);}
inline void print(ll a){printf("%lld\n",a);}
inline void print(ll a,ll b){printf("%lld %lld\n",a,b);}
inline void print(std::string s){std::cout << s << "\n";}
inline void print_yn(bool flg){if(flg){printf("Yes\n");}else{printf("No\n");}}

using namespace std;

int main() {
  ll h, w, n;
  scan(h, w, n);
  vvi obj(w);
  rep (i, n) {
    int x, y;
    scan(x, y);
    if (x < y) { continue; }
    x -= 1; y -= 1;
    obj[y].push_back(x);
  }
  rep (i, w) {
    sort(all(obj[i]));
    obj[i].push_back(h);
  }
  int ans = obj[0][0];
  int fastest = 0;
  FOR (y, 1, w) {
    int emp = fastest + 1;
    for (int x : obj[y]) {
      if (x < emp) { continue; }
      if (emp == x) {
        emp += 1;
      } else {
        ans = min(ans, x);
        fastest = emp;
        break;
      }
    }
  }
  print(ans);

  return 0;
}


Measured memory_bytes: 11264