725 B | 725 chars
#include <bits/stdc++.h>
using namespace std;
typedef unsigned long long ull;
typedef long long ll;
typedef vector <ll> llv1;
typedef unsigned int uint;
typedef vector <ull> ullv1;
typedef vector <vector <ull>> ullv2;
ll X,Y,N,ax,ay,bx,by,ans;
bool check[330][330];
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> X >> Y >> N;
for(int t = 0; t < N; t++) {
cin >> ax >> ay >> bx >> by;
for(int x =ax; x<=bx; x++) {
for(int y=ay;y<=by; y++) {
check[x][y] = true;
}
}
}
for(int x=0; x<=X; x++) {
for(int y=0; y<=Y; y++) {
if(check[x][y]) ans++;
}
}
cout << ans;
}