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#include <bits/stdc++.h>

using namespace std;


#define _DEBUG
#ifdef _DEBUG
template<typename T1, typename T2> auto& operator<<(ostream& o, pair<T1, T2> a) { return o << "(" << a.first << ", " << a.second << ")"; }
template<typename T, typename OS> auto& operator<<(OS& o, T a) { o << "{"; for (auto b : a) o << b << ", "; return o << "}"; }
#define dbg(x...) cerr << "[" #x "]: ", [](auto... args) { ((cerr << args << ", "),...) << "\n"; }(x)
#else
#define dbg(...)
#endif

#define sz(x) ((int)(x).size())
#define all(x) (x).begin(), (x).end()
#define F first
#define S second
#define db cerr << "\033[91m"

using ll = long long;
using ld = long double;
using pll = pair<ll,ll>;
using vi = vector<int>;

int main() {
    cin.tie(0)->sync_with_stdio(0);

    ll n, m, s;
    cin >> n >> m >> s;
    vector<pll> p(m);
    for(ll i = 0 ; i < m ; ++i) cin >> p[i].F >> p[i].S;
    sort(all(p));
    ll ans = -1;


    for(ll i = 0 ; i < m ; ++i) {
        if((i == 0 || p[i-1].S != p[i].F-1) && p[i].F != 1) {
            ll x = p[i].F-1;
            if(ans == -1 || abs(x-s) < abs(ans-s)) ans = x;
        }
        if((i == n-1 || p[i+1].F != p[i].S+1) && p[i].S != n) {
            ll x = p[i].S+1;
            if(ans == -1 || abs(x-s) < abs(ans-s)) ans = x;
        }
    }
    cout << ans << '\n';


    return 0;
}