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UVa 10763.cpp
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UVa 10763.cpp
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/*BISMILLAHIR RAHMANIR RAHIM*/
#include<bits/stdc++.h>
#define lli long long int
#define yes cout << "YES\n"
#define no cout << "NO\n"
#define ALL(x) x.begin(), x.end()
#define print(x) cout<<x<<endl;
#define PI acos(-1.0)
#define nl cout<<"\n"
#define mem(ar, val) memset(ar, val, sizeof(ar))
#define point(x) fixed<<setprecision(x)
#define printcase(n) cout << "Case " << tc << ": " << n <<endl
#define printcaseii(n, m) cout << "Case " << tc << ": " << n << " " << m <<endl
#define aInput(ar, n) for(int i=0; i<n; i++)cin>>ar[i];
#define vInput(v, n) for(int i=0; i<n; i++){lli x;cin>>x;v.push_back(x);}
#define input2D(ar, row, col) for(int i=0; i<row; i++){for(int j=0; j<col; j++){cin >> ar[i][j];}}
#define print2D(ar, row, col) for(int i=0; i<row; i++){for(int j=0; j<col; j++){cout << ar[i][j] << " ";}cout<<endl;}
#define vprint(vec) for(int i=0; i<vec.size(); i++){cout << vec[i]; (i==vec.size()-1? cout<<endl : cout<<" ");}
#define aprint(ar, n) for(int i=0; i<n; i++){cout << ar[i] << " ";}cout<<endl
#define ANUPAM_AKIB ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL)
#define execution_time cerr<<endl;int z=30;while(z--){cerr<<'-';}cerr<<endl;cerr<<point(16)<<"**Time -> "<<(double)(clock()-tStart)/CLOCKS_PER_SEC<<"fs"<<endl;
#define INPUT freopen("input.txt", "r", stdin)
#define OUTPUT freopen("output.txt", "w", stdout)
#define yo(x) cerr<<(#x)<<" = "<<(x)<<endl;
#define ff first
#define ss second
using namespace std;
const lli inf = INT_MAX;
const int mod = 20000;
lli findLCM(lli a, lli b){return ((a*b)/__gcd(a,b));}
lli input(){lli x; cin >> x; return x;}
int digitCNT(int n){return ceil(log10(n)+0.00000001);}
bool cmp(lli a, lli b){return a>b;}
int adj[1000][1000];
void solve(int tc){
int a, b;
mem(adj, 0);
vector<pair<int, int> > v;
for(int i=0; i<tc; i++){
cin >> a >> b;
v.push_back({a, b});
if(adj[b][a]){
adj[b][a]--;
}
else{
adj[a][b]++;
}
}
bool hobe = true;
for(auto p : v){
a = p.first, b = p.second;
if(adj[a][b] or adj[b][a]){
hobe = false; break;
}
}
hobe? yes : no;
}
int main(){
ANUPAM_AKIB;
#ifndef ONLINE_JUDGE
clock_t tStart = clock();
//INPUT;
//OUTPUT;
#endif
int tc = 1;
//cin >> tc; //TEST CASE
//for(int i=1; i<=tc; i++){
// solve(i);
//}
while(cin>>tc){
if(tc==0) break;
solve(tc);
}
#ifndef ONLINE_JUDGE
execution_time;
#endif
return EXIT_SUCCESS;
}