//double half = N*1.0/2;

int half = ceil(N*1.0/2);

set<int>::iterator it;

int min_moves = INF;

for(it = colors.begin(); it!=colors.end(); it++){

//cout<<"seeing "<<*it<<endl;

//cout<<"up is "<<up[*it]<<" down is "<<down[*it]<<" cnt_same is "<<count_same[*it]<<endl;

if( up[*it] >= half ){

min_moves = min(min_moves, 0);

}else if( up[*it] + down[*it] - count_same[*it] >= half){

//cout<<"in "<<endl;

int need_flip = half - up[*it];

//min_moves = min(min_moves, down[*it] - count_same[*it]);

min_moves = min(min_moves, need_flip);

}

}

if(min_moves == INF){

cout<<"-1"<<endl;

}else{

cout<<min_moves<<endl;

}

cin>>N;

int f, s;

for(int i=0; i<N; i++){

cin>>f>>s;

if(up.find(f)==up.end()){

up[f]=1;

}else{

up[f]++;

}

if(down.find(s) == down.end()){

down[s] = 1;

}else{

down[s]++;

}

colors.insert(f);

colors.insert(s);

if(s==f){

if( count_same.find(s)!=count_same.end() ){

count_same[s] += 1;

}else{

count_same[s] = 1;

}

}

}

work();

return 0;