this is my code:
#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
using namespace std;
int main()
{
    vector <int> A;
    vector <int> B;
    int a,b,n;
    cin>>n;
    for(int i=0; i<n; i++)
    {
        cin>>a>>b;
        A.push_back(a);
        B.push_back(b);
    }
    sort(A.begin(),A.end());
    sort(B.begin(),B.end());
    a=1;
    b=a;
    for(int i=1; i<n; i++)
    {
    if(A[i]!=A[i-1]) a++;
    if(B[i]!=B[i-1]) b++;
    }
    cout<<min(a,b);
    system("pause");
    return 0;
}

Test
---
3
1 10
2 11
3 12
---
Your answer is 3, expected is 1