#include <iostream>
#include <algorithm>
#include <vector>
#include <climits>

using namespace std;

bool pairComp(const pair<int, int>& a, const pair<int, int>& b) {
    return a.first < b.first;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    int n;
    int m;
    int s;

    cin >> n >> m >> s;

    vector<pair<int, int>> occupied;

    int a, b;
    for (int i = 0; i < m; i++) {
        cin >> a >> b;
        occupied.push_back({ a, b });
    }

    sort(occupied.begin(), occupied.end(), pairComp);

    occupied.insert(occupied.begin(), { -1, 0 });
    occupied.push_back({ n + 1, n + 2 });

    int nearest =  -1;
    int val = INT_MAX;

    for (int i = 1; i < m + 1; i++) {
        if (occupied[i-1].second != occupied[i].first - 1) {
            int dist = abs(occupied[i].first - 1 - s);
            if (dist < val) {
                nearest = occupied[i].first - 1;
                val = dist;
            }
        }

        if (occupied[i].second + 1 != occupied[i + 1].first) {
            int dist = abs(occupied[i].second + 1 - s);
            if (dist < val) {
                nearest = occupied[i].second + 1;
                val = dist;
            }
        }
    }

    cout << nearest;
}