Tietoverkko

input/code.cpp: In function 'int findv(int)':
input/code.cpp:11:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0; i<v.size(); i++) {
                ^
input/code.cpp: In function 'void removesingle()':
input/code.cpp:28:16: error: expected primary-expression before '==' token
     if(w[i+1]) == 1) c = 1;
                ^
input/code.cpp:34:16: error: expected primary-expression before '==' token
     if(w[i-1]) == 1) c = 1;
                ^

#include <bits/stdc++.h>

using namespace std;

int n;
int p = 0;
vector<int> v;
vector<int> w;

int findv(int x) {
	for(int i=0; i<v.size(); i++) {
		if(v[i]==x) {
			return i;		
		}	
	}
	return -1;
}

void removesingle() {
	int c = 0;
	for(int i = 0; i<n+1; i++) {
		if(w[i] == 1) { 
			p++;
			int pos = findv(i);
			w[i]--;
			if(pos%2==0) {
				w[i+1]--;
				if(w[i+1]) == 1) c = 1;
				v.erase(v.begin()+pos);
				v.erase(v.begin()+pos+1);
			}
			else {
				w[i-1]--;
				if(w[i-1]) == 1) c = 1;
				v.erase(v.begin()+pos);
				v.erase(v.begin()+pos-1);
			}
		}
	}
	if(c==0) return;
	removesingle();
}

int main() {
	cin.tie(0);
	ios_base::sync_with_stdio(0);

	cin >> n;
	for(int i = 0; i<n+1; i++) w.push_back(0);
	for(int i = 0; i<(n*2); i++) {
		int t; cin >> t;
		v.push_back(t);		
		w[t]++;	
	}
	
	removesingle();
	
	cout << p << endl;
}