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#include <bits/stdc++.h>
using namespace std;
pair<long long,long long>wyn={numeric_limits<long long>::max(),0};
void Kand(long long x, long long s)
{
    wyn=min(wyn,pair<long long,long long>{abs(x-s),x});
}
int main()
{ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    long long n,s;
    int m;
    cin>>n>>m>>s;
    vector<pair<long long,long long>>U;
    U.push_back({0,0});
    U.push_back({n+1,n+1});
    for(int i=1;i<=m;i++)
    {
        long long a,b;
        cin>>a>>b;
        U.push_back({a,b});
    }
    sort(U.begin(),U.end());
    for(int i=1;i+1<U.size();i++)
    {
        if(U[i-1].second+1!=U[i].first)
        {
            Kand(U[i].first-1,s);
        }
        if(U[i+1].first-1!=U[i].second)
        {
            Kand(U[i].second+1,s);
        }
    }
    cout<<wyn.second<<'\n';
    return 0;
}