题解

#include<bits/stdc++.h>
using namespace std;
int main(){
    int n,m,a,q,minn=20000,b;
    cin>>n>>m>>a>>q;
    for(int i=1;i<=q;i++){
        cin>>b;
        minn=min(minn,b);
    }
    long long mj=(n-a)*(m-minn);
    cout<<mj;
    return 0;
}