1 #include<iostream>
 2 #include<cstdio>
 3 
 4 using namespace std;
 5 
 6 int n,k,cf[1004][1004],ans,a[1004][1004]; 
 7 
 8 int main() {
 9     scanf("%d%d",&n,&k);
10     for(int i = 1;i <= n; i++) {
11         int x,y,xx,yy;
12         scanf("%d%d%d%d",&x,&y,&xx,&yy);
13         cf[x][y]++;
14         cf[xx][y]--;
15         cf[x][yy]--;
16         cf[xx][yy]++;
17     }
18     for(int i = 0;i <= 1001; i++)
19         for(int j = 0;j <= 1001; j++) {
20             a[i][j] = a[i-1][j] + a[i][j-1] - a[i-1][j-1] + cf[i][j];
21             if(a[i][j] == k) ans++;
22         }
23     printf("%d",ans);
24     return 0;
25 }