#include <bits/stdc++.h>
#include <random>

using namespace std;

typedef unsigned long long ull;
typedef long long ll;
typedef double ld;
//#define ll __int128
#define int ll
//#define int ll
//#define char ll
typedef vector<char> vc;
typedef vector<vc> vvc;
typedef vector<vvc> vvvc;
typedef pair<int, int> pii;
typedef pair<pii, pii> piii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<pii> vpi;
typedef vector< vi > vvi;
typedef vector< vvi > vvvi;
typedef vector<short> vs;
typedef vector<vs> vvs;
typedef vector<vvs> vvvs;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
typedef vector<ld> vld;
typedef vector<vld> vvld;
typedef vector<vvld> vvvld;
typedef vector<string> vst;
typedef vector<vst> vvst;
typedef pair<ld, ld> pld;

#define inmin(a, b) a = min(a, (b))
#define inmax(a, b) a = max(a, (b))
#define ALL(a) a.begin(),a.end()
#define RALL(a) a.rbegin(),a.rend()
#define sqr(x) ((x) * (x))
#define fori(i, n) for(int i = 0; i < int(n); ++i)
#define SZ(a) ((int)((a).size()))
#define triple(T) tuple<T, T, T>
#define quad(T) tuple<T, T, T, T>
#define watch(x) cerr << (#x) << " = " << (x) << endl;

#ifdef MAX_HOME
#define cerr cout
#else
#define cerr if (false) cerr
#endif

const double PI = 2 * acos(0.0);
#define rand shittttty_shit
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rng_64(chrono::steady_clock::now().time_since_epoch().count());

const string DIGITS = "0123456789";
const string ALPH = "abcdefghijklmnopqrstuvwxyz";


template <class T0, class T1>
inline ostream & operator << (ostream &out, pair<T0, T1> &a) {
    return out << "{" << a.first << ", " << a.second << "}";
}

template <class T0, class T1>
inline istream & operator >> (istream &in, pair<T0, T1> &a) {
    return in >> a.first >> a.second;
}

template <class T0, class T1, class T2>
inline ostream & operator << (ostream &out, tuple<T0, T1, T2> &a) {
    return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a) << "}";
}

template <class T0, class T1, class T2, class T3>
inline ostream & operator << (ostream &out, tuple<T0, T1, T2, T3> &a) {
    return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a) << ", " <<  get<3>(a) << "}";
}

template<class T>
inline ostream & operator << (ostream &out, vector<T> &a) {
    out << "[";
    fori (i, a.size())
        out << a[i] << vector<string>{", ", "]  "}[i + 1 == a.size()];
    return out;
}


void smain();



signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

#ifdef MAX_HOME
    freopen("input.txt", "r", stdin);
    clock_t start = clock();
#endif
    cout << setprecision(4) << fixed;
    smain();
#ifdef MAX_HOME
    cout << "\n\n\n\nTOTAL EXECUTION TIME: " << float( clock () - start ) /  CLOCKS_PER_SEC << endl;
#endif
    return 0;
}

int ansA, ansT;
const int oo = 1e9 + 10;

const int N = 2e5 + 10;

int bnd[N];

void smain() {
    int n, m, q;
    cin >> n >> m >> q;
    ansA = oo;
    ansT = oo;

    vector<pii> qrs(q);


    fori (i, q) {
        cin >> qrs[i].first >> qrs[i].second;
    }

    set<pii> qset(ALL(qrs));

    int x0 = 2, y0 = 1;

    fill(bnd, bnd + N, oo);
    bnd[1] = 1;
    bool prv = false;
    while (x0 <= n && !qset.count({x0, y0})) {
        int x1 = x0, y1 = y0 + 1;
        if (!prv && y1 <= m && !qset.count({x1, y1})) {
            x0 = x1;
            y0 = y1;
            prv = true;
        } else {
            prv = false;
            x0 += 1;
        }

        inmin(bnd[y0], x0);
    }


    fori (i, q) {
        int x, y;
        x = qrs[i].first, y = qrs[i].second;
        --x;
        if (x >= bnd[y]) {
            int cT = x - 1;
            int cA = y - 1;
            cA += cT - cA;
            cT++;
            if (x == bnd[y]) {
                cA++;
            }
            if (cA < ansA || cA == ansA && cT < ansT) {
                ansA = cA;
                ansT = cT;
            }
        }
    }
    for (int y = 1; y <= m; ++y) {
        int x = n;
        if (x >= bnd[y]) {
            int cT = x - 1;
            int cA = y - 1;
            cA += cT - cA;
            cT++;
            if (x == bnd[y]) {
                cA++;
            }
            if (cA < ansA || cA == ansA && cT < ansT) {
                ansA = cA;
                ansT = cT;
            }
        }
    }
    cout << ansT;
}

Measured memory_bytes: 17408