1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
// clang-format off
#include<bits/stdc++.h>
using namespace std;
using LL=long long;
#define FOR(i,l,r) for(auto i=(l);i<=(r);++i)
#define REP(i,n) FOR(i,0,(n)-1)
#define ssize(x) int(x.size())
template<class A,class B>auto&operator<<(ostream&o,pair<A,B>p){return o<<"("<<p.first<<", "<<p.second<<")";}
template<class T>auto operator<<(ostream&o,T x)->decltype(x.end(),o){o<<"{";int i=0;for(auto e:x)o<<(", ")+2*!i++<<e;return o<<"}";}
#ifdef DEBUG
#define debug(X...)cerr<<"["#X"]: ",[](auto...$){((cerr<<$<<"; "),...)<<"\n";}(X)
#else
#define debug(...) {}
#endif
// clang-format on

int
main()
{
    cin.tie(0)->sync_with_stdio(0);
    LL N, M, S;
    cin >> N >> M >> S;
    vector<pair<LL, LL>> rs(M);
    for (auto& r : rs) cin >> r.first >> r.second;
    sort(rs.begin(), rs.end());
    debug(rs);

    // Find school
    auto sr = prev(lower_bound(rs.begin(), rs.end(), make_pair(S + 1, 0LL)));
    debug(S, *sr);

    // Try to go right
    auto right = sr;
    while (next(right) < rs.end() && right->second + 1 == next(right)->first)
        ++right;

    // Try to go left
    auto left = sr;
    while (left > rs.begin() && prev(left)->second + 1 == left->first) --left;

    // Obtain candidate
    pair<LL, LL> best = {numeric_limits<LL>::max(), numeric_limits<LL>::max()};
    if (left->first > 1)
        best = min(best, make_pair(S - left->first, left->first - 1));
    if (right->second < N)
        best = min(best, make_pair(right->second - S, right->second + 1));
    cout << best.second << "\n";
    return 0;
}