#include <bits/stdc++.h>

using namespace std;

#define rep(i, a, b) for (int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int) (x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;

void solve() {
    int n, k, q; cin >> n >> k >> q;
    --k;
    vector<pii> a(q);
    rep(i, 0, q) {
        int l, r; cin >> l >> r;
        --l, --r;
        a[i] = pii(l, r);
    }
    reverse(all(a));
    for (auto [l, r] : a) {
        if (k >= l && k <= r) {
            k = l + r - k;
        }
    }
    cout << k + 1 << "\n";
}

signed main() {
    ios::sync_with_stdio(false); cin.tie(nullptr);

    solve();

    return 0;
}