Language: C++

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

#define fastio 			ios::sync_with_stdio(0);	cin.tie(0); cout.tie(0);  cout<<fixed;  cout<<setprecision(12);
#define randomINT 		mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
#define	newl 			cout<<"\n"
#define DISP(as)		for(auto it : as) cout<<it<<" ";newl;
#define all(x)         	(x).begin(),(x).end()
#define mset(x,val)    	memset(x,val,sizeof(x))
#define newl           	cout<<"\n"
#define pb             	push_back
#define mp             	make_pair
#define f 				first
#define s 				second
#define dline          cerr<<"///REACHED///\n";
#define deb1(x)        cerr<<#x<<" = "<<x<<'\n';
#define deb2(x,y)      cerr<<'['<<#x<<','<<#y<<"] = "<<'['<<x<<','<<y<<']'<<'\n';
#define deb3(x,y,z)    cerr<<'['<<#x<<','<<#y<<','<<#z<<"] = "<<'['<<x<<','<<y<<','<<z<<']'<<'\n';

typedef long long 				ll;
typedef long double 			ld;
typedef vector<ll> 				vll;
typedef pair<ll , ll> 			pll;
typedef pair<ld, ld> 			pld;
typedef unordered_map<ll, ll> 	um;
typedef vector<pll> 			vpll;

const ll 	MAX5 	= 	1e+5 + 7;
const ll 	MAX7 	= 	1e+7 + 7;
const ll 	MAXN 	= 	MAX7;
const ll   	INF   	=  	0x7f7f7f7f7f7f7f7f;
const int  	INFi 	=  	0x7f7f7f7f;
const ll 	MOD		=  	1e9 + 7;


// <------------- Declare Variables Here ------------> //

ll T = 1;
ll n, x, k, p;
string s, t;

// <------------- Implement Functions Here ----------> //

// <------------- Start of main() -------------------> //

void MAIN() {
	cin>>n;
	vpll a;
	for(ll i=0;i<n;i++) {
		cin>>x>>k;
		a.pb({x,y});
	}
	sort(all(a));
	reverse(all(a));

	cout<<a[0].f + a[0].s;
}

int main() {
	fastio; randomINT;
	//cin >> T;
	while (T--) {
		MAIN();
	}
	return 0;
}

Compiler output:
a.cc: In function 'void MAIN()':
a.cc:51:25: error: 'y' was not declared in this scope
   51 |                 a.pb({x,y});
      |                         ^
a.cc:51:21: error: no matching function for call to 'std::vector<std::pair<long long int, long long int> >::push_back(<brace-enclosed initializer list>)'
   51 |                 a.pb({x,y});
      |                 ~~~~^~~~~~~
In file included from /usr/include/c++/14/vector:66,
                 from /usr/include/c++/14/functional:64,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:53,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_vector.h:1283:7: note: candidate: 'void std::vector<_Tp, _Alloc>::push_back(const value_type&) [with _Tp = std::pair<long long int, long long int>; _Alloc = std::allocator<std::pair<long long int, long long int> >; value_type = std::pair<long long int, long long int>]'
 1283 |       push_back(const value_type& __x)
      |       ^~~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1283:35: note:   no known conversion for argument 1 from '<brace-enclosed initializer list>' to 'const std::vector<std::pair<long long int, long long int> >::value_type&' {aka 'const std::pair<long long int, long long int>&'}
 1283 |       push_back(const value_type& __x)
      |                 ~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_vector.h:1300:7: note: candidate: 'void std::vector<_Tp, _Alloc>::push_back(value_type&&) [with _Tp = std::pair<long long int, long long int>; _Alloc = std::allocator<std::pair<long long int, long long int> >; value_type = std::pair<long long int, long long int>]'
 1300 |       push_back(value_type&& __x)
      |       ^~~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1300:30: note:   no known conversion for argument 1 from '<brace-enclosed initializer list>' to 'std::vector<std::pair<long long int, long long int> >::value_type&&' {aka 'std::pair<long long int, long long int>&&'}
 1300 |       push_back(value_type&& __x)
      |                 ~~~~~~~~~~~~~^~~