171227_2563_색종이

//https://www.acmicpc.net/problem/2563

#include <iostream>

using namespace std;

bool paper[100][100];

int main()

{

int n,ans,x,y;

cin >> n;

ans=0;

for(int i=0 ; i<n; i++)

{

cin >> x >> y;

for(int j=0; j<10; j++)

for(int k=0; k<10; k++)

{

if(!paper[y+j][x+k]) ans++;

else continue;

paper[y+j][x+k]=1;

}

}

cout << ans;

}