UVA 10963 The Swallowing Ground Solution

///     Raihan Ruhin
///     CSE, Jahangirnagar University.
///     Dhaka-Bangladesh.
///     id: raihanruhin (topcoder / codeforces / codechef / hackerrank / uva / uvalive, spoj), 3235 (lightoj)
///     mail: raihanruhin@ (yahoo / gmail / facebook)
///     blog: ruhinraihan.blogspot.com

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

#define SET(a) memset(a,-1,sizeof(a))
#define CLR(a) memset(a,0,sizeof(a))
#define PI acos(-1.0)

#define MOD 1000000007
#define MX 100010


int main()
{
    ios_base::sync_with_stdio(0);cin.tie(0);
    int n, tc, kk=1, x, y;
    string s;
    cin>>tc;
    while(tc--)
    {
        cin>>n;
        set<int>st;
        for(int i=0;i<n;i++)
        {
            cin>>x>>y;
            st.insert(abs(x-y));
        }
        if(kk>1) cout<<"\n";
        if(st.size()==1) cout<<"yes\n";
        else cout<<"no\n";
        kk++;
    }
return 0;
}