Language: C++

#define ll long long
#define dd long double
#define pub push_back
#define pob pop_back
#define puf push_front
#define pof pop_front
#define mp make_pair
#define mt make_tuple
#define fo(i , n) for(ll i = 0 ; i < n ; i++)
//#include<bits/stdc++.h>
#include<iomanip>   
#include<cmath>
#include<cstdio>
#include<utility>
#include<iostream>
#include<vector>
#include<string>
#include<algorithm>
#include<map>
#include<queue>
#include<set>
#include<stack>
#include<bitset>
dd pi = acos(-1) ;
ll z =  1000000007 ;
ll inf = 100000000000000000 ;
ll p1 = 37 ;
ll p2 = 53 ;
ll mod1 =  202976689 ;
ll mod2 =  203034253 ;
ll fact[100] ;
ll gdp(ll a , ll b){return (a - (a%b)) ;}
ll ld(ll a , ll b){if(a < 0) return -1*gdp(abs(a) , b) ; if(a%b == 0) return a ; return (a + (b - a%b)) ;} // least number >=a divisible by b
ll gd(ll a , ll b){if(a < 0) return(-1 * ld(abs(a) , b)) ;    return (a - (a%b)) ;} // greatest number <= a divisible by b
ll gcd(ll a , ll b){ if(b > a) return gcd(b , a) ; if(b == 0) return a ; return gcd(b , a%b) ;}
ll e_gcd(ll a , ll b , ll &x , ll &y){ if(b > a) return e_gcd(b , a , y , x) ; if(b == 0){x = 1 ; y = 0 ; return a ;}
ll x1 , y1 ; e_gcd(b , a%b , x1 , y1) ; x = y1 ; y = (x1 - ((a/b) * y1)) ; return e_gcd(b , a%b , x1 , y1) ;}
ll power(ll a ,ll b , ll p){if(b == 0) return 1 ; ll c = power(a , b/2 , p) ; if(b%2 == 0) return ((c*c)%p) ; else return ((((c*c)%p)*a)%p) ;}
ll inverse(ll a ,ll n){return power(a , n-2 , n) ;}
ll max(ll a , ll b){if(a > b) return a ; return b ;}
ll min(ll a , ll b){if(a < b) return a ; return b ;}
ll left(ll i){return ((2*i)+1) ;}
ll right(ll i){return ((2*i) + 2) ;}
ll ncr(ll n , ll r){if(n < r|| (n < 0) || (r < 0)) return 0 ; return ((((fact[n] * inverse(fact[r] , z)) % z) * inverse(fact[n-r] , z)) % z);}
void swap(ll&a , ll&b){ll c = a ; a = b ; b = c ; return ;}
//ios_base::sync_with_stdio(0);
//cin.tie(0); cout.tie(0);
using namespace std ;
/*#include <ext/pb_ds/assoc_container.hpp> 
#include <ext/pb_ds/tree_policy.hpp> */
using namespace __gnu_pbds; 
//#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
// ordered_set s ; s.order_of_key(val)  no. of elements strictly less than val
// s.find_by_order(i)  itertor to ith element (0 indexed)
//__builtin_popcount(n) -> returns number of set bits in n
// ll seed;
//mt19937 rnd(seed=chrono::steady_clock::now().time_since_epoch().count()); // include bits
void solve()
{
    ll h , w , m ;
    cin >> h >> w >> m ;
    ll max_r = 0 , max_c = 0 ;
    map<ll ,ll> row , col ;
    map<pair<ll ,ll> , ll> v ;
    fo(i , m)
    {
        ll x , y ;
        cin >> x >> y ;
        pair<ll ,ll> g = mp(x , y) ;
        v[g] = 1 ;
        row[x]++ ;
        col[y]++ ;
        max_r = max(max_r , row[x]) ;
        max_c = max(max_c , col[y]) ;
    }
    //cout << max_r << ' ' << max_c << endl ;
    vector<ll> mrow , mcol ;

    for(auto itr = row.begin() ; itr != row.end() ; itr++)
    {
        if((itr->second) == max_r)
            mrow.pub(itr->first) ;
    }

    for(auto itr = col.begin() ; itr != col.end() ; itr++)
    {
        if((itr->second) == max_c)
        {
            //cout << (itr -> first) << endl ;
            mcol.pub(itr->first) ;
        }
    }

    ll flag = 1 ;

    fo(i , mrow.size())
        fo(j , mcol.size())
        {
            pair<ll ,ll> g = mp(mrow[i] , mcol[j]) ;
            if(v[g] == 0)
            {
                flag = 0 ;
                break ;
            }
        }
    
    cout << max_r + max_c - flag << endl ;
    return  ;
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
   /* #ifndef ONLINE_JUDGE
    freopen("inputf.txt" , "r" , stdin) ;
    freopen("outputf.txt" , "w" , stdout) ;
    freopen("error.txt" , "w" , stderr) ;
    #endif*/
    
    ll t ;
    //cin >> t ;
    t = 1 ;
   
    while(t--)
    {
        solve() ;
    }
    cerr << "Time : " << 1000 * ((double)clock()) / (double)CLOCKS_PER_SEC << "ms\n";
 
    return 0;
}


Compiler output:
a.cc:51:17: error: '__gnu_pbds' is not a namespace-name
   51 | using namespace __gnu_pbds;
      |                 ^~~~~~~~~~