/*
#include <stdio.h>
int main()
{
int arr[100][100]= {};
int n,m,i,j;
scanf("%d %d",&n,&m);
int x=n-1,y=0,dir=0,k=n*m;
while(k>0)
{
arr[x][y]=k;
if(dir==0)
{
x--;
}
else if(dir==1)
{
y++;
}
else if(dir==2)
{
x++;
}
else if(dir==3)
{
y--;
}
if (x < 0 || x >= n || y < 0 || y >= m || arr[x][y] != 0)
{
if (dir == 0)
{
x++;
}
else if (dir == 1)
{
y--;
}
else if (dir == 2)
{
x--;
}
else if (dir == 3)
{
y++;
}
dir = (dir + 1) % 4;
if (dir == 0)
{
x--;
}
else if (dir == 1)
{
y++;
}
else if (dir == 2)
{
x++;
}
else if (dir == 3)
{
y--;
}
}
k--;
}
for(i=0; i<n; i++)
{
for(j=0; j<m; j++)
{
printf("%d ",arr[i][j]);
}
printf("\n");
}
return 0;
}
*/
#include <stdio.h>
int main()
{
int arr[101][101]= {};
int n,k,i,j,x,y,a;
scanf("%d",&n);
for(k=0; k<n; k++)
{
scanf("%d %d",&x,&y);
}
for(i=x; i<x+10; i++)
{
for(j=y; j<y+10; j++)
{
arr[i][j]=1;
}
}
for(i=0; i<100; i++)
{
for(j=0; j<100; j++)
{
if(arr[i][j]=1)
{
a++;
}
}
}
return 0;
}