为什么一用longlong就显示编译错误？

#include <bits/stdc++.h>
using namespace std;
int main (){
    int n,bx,by,cx,cy,a,b,xx,yy,ax,ay;
    long long maxx=-1000000000,minx=1000000000,maxy=-1000000000,miny=1000000000;
    cin >> n;
    for (int i=1; i<=n; i++) {
        cin >> bx>> by>> cx>> cy;
        xx=max(bx,cx); yy=max(by,cy);
        ax=min(bx,cx); ay=min(by,cy);
        maxx=max(maxx,xx);minx=min(minx,ax);
        maxy=max(maxy,yy);miny=min(miny,ay);
        }
    a= maxx-minx; b=maxy-miny;
    cout << a*b;
    return 0;
}