#include <iostream>
#include <vector>
#include <cmath>
#include <cstring>
#include <queue>
#include <algorithm>
using namespace std;

//pair<int,int> PP;

vector< pair< int , pair<int, int > > > vban,zban;
int BAD[210][210];
vector<pair<int,int> > P;
int N;

queue<int> Q;

int dx[4] = {0,0,-1,1};
int dy[4] = {-1,1,0,0};

void bfs(int sx,int sy){
	while(!Q.empty()) Q.pop();
	Q.push(sx); Q.push(sy);
	while (!Q.empty()){
		int px = Q.front(); Q.pop();
		int py = Q.front(); Q.pop();

		// (px == 105 && py == 105) cout << "tu" << endl;

		for (int i=0;i<4;i++){
			int tx = px + dx[i];
			int ty = py + dy[i];
		

			if (tx < 0 || tx > 202) continue;
			if (ty < 0 || ty > 202) continue;
			if (BAD[tx][ty] != 0) continue;
			if (i > 1){
				//vodorovne bany

				if (i == 2){
					int wrong = 0;
				for(int j=0;j<vban.size();j++){
					if (vban[j].first == px){
						if (ty >= vban[j].second.first && ty < vban[j].second.second ){ wrong = 1; break;}
					}

				}
				if (wrong == 1) continue;
			
				}else{
					int wrong = 0;
					for(int j=0;j<vban.size();j++){
						if (vban[j].first == px+1){
							if (ty >= vban[j].second.first && ty < vban[j].second.second ){ wrong = 1; break;}
						}
					}
					if (wrong == 1) continue;
			
				}

			}else{
				//zvisle bany
				
				if ( i == 0){
				int wrong = 0;
				for(int j=0;j<zban.size();j++){
					//cout << "zban!" << zban[j].first << endl;
					if (zban[j].first == py  ){
						if (tx >= zban[j].second.first && tx < zban[j].second.second ){ wrong = 1; break;}
					}
				}
				if (wrong == 1) continue;


				}else{
			
				int wrong = 0;
				for(int j=0;j<zban.size();j++){
					//cout << "zban!" << zban[j].first << endl;
					if (zban[j].first == py+1  ){
						if (tx >= zban[j].second.first && tx < zban[j].second.second ){ wrong = 1; break;}
					}
				}
				if (wrong == 1) continue;


				}
			}
			BAD[tx][ty] = 1;
			Q.push(tx); Q.push(ty);
		}

	}
	return;
}

int main(){

	while (true){
		cin >> N;
		if (N == 0) break;
		P.resize(N);
		for (int i=0;i<N;i++){
			int x,y;
			cin >> x >> y;
			x+= 102; y+= 102;
			P[i] = make_pair(x,y);
		}

		vban.resize(0);
		zban.resize(0);
		memset(BAD,0,sizeof(BAD));

		for (int i=0;i<N;i++){
			if (P[i].first == P[(i+1)%N].first){
				//zvisle
				if (P[i].second < P[(i+1)%N].second){
					zban.push_back( make_pair( P[i].first, make_pair( P[i].second, P[(i+1)%N].second)  )  );
					
				}else{
					zban.push_back( make_pair( P[i].first, make_pair( P[(i+1)%N].second, P[i].second)  )  );
				}
				continue;
			}
			if (P[i].second == P[(i+1)%N].second){
				//vodorovne
				
				if (P[i].first < P[(i+1)%N].first){
	 				vban.push_back( make_pair( P[i].second, make_pair( P[i].first, P[(i+1)%N].first)  )  );
				}else{
					vban.push_back( make_pair( P[i].second, make_pair( P[(i+1)%N].first, P[i].first)  )  );
				}
				continue;
			}

			//ostatne
			pair<int ,int > dolny, horny;		
			if (P[i].second < P[(i+1)%N].second ){
				dolny = P[i];
				horny = P[(i+1)%N];
			}else{
				dolny = P[(i+1)%N];
				horny = P[i];
			}
			double delta = ( (double)(horny.first - dolny.first)/( horny.second - dolny.second ));
			double start = dolny.first;
			if (delta > 0.0){
				for(int j = dolny.second; j<horny.second;j++){
					for(int k = (int)start; k<=(int)(start+delta - 10e-5); k++){
//						cout << "setting bad " << j << " " << k << endl;
						BAD[j][k] = 1;
					}
					start += delta;
				}
			}else{
				for (int j=dolny.second; j<horny.second;j++){
					for(int k = (int)(start+delta); k<= (int)(start-10e-5); k++){
						BAD[j][k] = 1;	
//						cout << "setting bad dec " << j << " " << k << endl;

					}
					start += delta;
				}
			}
	
		}

//	for(int i=0;i<zban.size();i++){
//			cout << zban[i].first << " " << zban[i].second.first << " " << zban[i].second.second << endl;
//		}

		bfs(0,0);
		int ans = 0;
		for(int i=0;i<=201;i++)for(int j=0;j<=201;j++){
			if (BAD[i][j] == 0)ans++;	
		}

		cout << ans << endl;

	}

	return 0;
}