Language: C++

#include <iostream>
#include <vector>
#include <algorithm>
#include <set>
#include <map>
#include <utility>
#include <tuple>
#include <string>
#include <cctype>
#include <cstdio>
#include <math.h>
using f32 = float;
using f64 = double;
using f80 = __float80;
constexpr i64 INF = 1'010'000'000'000'000'017LL;

constexpr i64 MOD = 1'000'000'007LL;

constexpr f64 EPS = 1e-12;

constexpr f64 PI = asin(-1.0);
using namespace std;
using LL = long long;
using ULL = unsigned long long;
using vi = vector<int>;
using vb = vector<bool>;
using vvb = vector<vb>;
using vvi = vector<vi>;
using vs = vector<string>;
using vl = vector<ll>;
using vvl = vector<vl>;
using P = pair<int, int>;
using T = tuple<int, int, int>;
using vp = vector<P>;
#define rep(i, n) for (i64 i = 0; i < (int)(n); i++)
#define FOR(i, m, n) for (i64 i = m; i < n; i++)
#define SORT(x) sort(x.begin(), x.end())
#define REVE(x) reverse(x.begin(), x.end())
#define all(x) (x).begin(), (x).end()
#define fst first
#define mp make_pair
#define pb push_back
#define eb emplace_back
#define pob pop_back
#define sw swap
#define UP(x) transform(x.begin(), x.end(), x.begin(), ::toupper);
#define LOW(x) transform(x.begin(), x.end(), x.begin(), ::tolower);
struct initon
{
    initon()
    {
        cin.tie(0);
        ios::sync_with_stdio(false);
    };
};
template <class T>
inline bool chmax(T &a, T b)
{
    if (a < b)
    {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
inline bool chmin(T &a, T b)
{
    if (a > b)
    {
        a = b;
        return 1;
    }
    return 0;
}

int main()
{
    int a, b, c, d, n, m;
    cin >> n >> m;
    rep(i, m)
    {
        cin >> a, b;
        c = max(a, b);
        d = min(a, b);
    }
    cout << max(0, c - d + 1);
}

Compiler output:
a.cc:15:11: error: 'i64' does not name a type; did you mean 'f64'?
   15 | constexpr i64 INF = 1'010'000'000'000'000'017LL;
      |           ^~~
      |           f64
a.cc:17:11: error: 'i64' does not name a type; did you mean 'f64'?
   17 | constexpr i64 MOD = 1'000'000'007LL;
      |           ^~~
      |           f64
a.cc:30:19: error: 'll' was not declared in this scope; did you mean 'LL'?
   30 | using vl = vector<ll>;
      |                   ^~
      |                   LL
a.cc:30:21: error: template argument 1 is invalid
   30 | using vl = vector<ll>;
      |                     ^
a.cc:30:21: error: template argument 2 is invalid
a.cc:31:20: error: 'vl' was not declared in this scope; did you mean 'vs'?
   31 | using vvl = vector<vl>;
      |                    ^~
      |                    vs
a.cc:31:22: error: template argument 1 is invalid
   31 | using vvl = vector<vl>;
      |                      ^
a.cc:31:22: error: template argument 2 is invalid
a.cc: In function 'int main()':
a.cc:35:24: error: 'i64' was not declared in this scope; did you mean 'f64'?
   35 | #define rep(i, n) for (i64 i = 0; i < (int)(n); i++)
      |                        ^~~
a.cc:81:5: note: in expansion of macro 'rep'
   81 |     rep(i, m)
      |     ^~~
a.cc:81:9: error: 'i' was not declared in this scope
   81 |     rep(i, m)
      |         ^
a.cc:35:35: note: in definition of macro 'rep'
   35 | #define rep(i, n) for (i64 i = 0; i < (int)(n); i++)
      |                                   ^