#include<cstdio>#include<iostream>#define NUM 100using namespace std;int main(){    int n,a[105][105] = {0};    cin >> n;    while(n--)    {        int x1,x2,y1,y2;        cin >> x1 >> y1 >> x2 >> y2;        for(int i = x1+1;i <= x2;i++)        {            for(int j = y1+1;j <= y2;j++)   a[i][j] = 1;        }    }    int num = 0;    for(int i = 1;i <= NUM;i++)    {        for(int j = 1;j <= NUM;j++)        {            if(a[i][j]) num++;        }    }    cout << num << endl;    return 0;}