#include <bits/stdc++.h>
using namespace std; 

#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define FOR(i, a, b) for( int i = a; i < (b); i++ )

using ll = long long;
using pii = pair<int, int>; 
using vi = vector<int>; 

void solve(){
    int n, q, k; cin >> n >> k >> q; 
    vector<pii> v(q); 
    for( auto &[l, r] : v ) cin >> l >> r; 
    reverse(all(v)); 
    
    for( auto [l, r] : v )
        if( l <= k && k <= r ) k = r - (k - l); 

    cout << k << '\n';
}

int main(){
    ios::sync_with_stdio(false); cin.tie(NULL); 
    solve(); 
}