题意：
a<=x<=b,c<=y<=d，求x*y==2018的(x,y)有多少对。
思路：
发现2018的因子只有1,2,1009,2018,然后选取两个区间的因子然后容斥一下就可以。
代码：
#include <iostream>
#include <iomanip>
#include <algorithm>
#include <cstring>
#include <cctype>
#include <cstdlib>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <map>
#include <list>
#include <set>
#include <stack>
#include <queue>
#include <string>
#include <sstream>
#define pb push_back
#define X first
#define Y second
#define lch (o<<1)
#define rch (o<<1|1)
#define ALL(x) x.begin(),x.end()
#define INS(x) inserter(x,x.begin())
#define pii pair<int,int>
#define qclear(a) while(!a.empty())a.pop();
#define lowbit(x) (x&-x)
#define sd(n) scanf("%d",&n)
#define sdd(n,m) scanf("%d%d",&n,&m)
#define sddd(n,m,k) scanf("%d%d%d",&n,&m,&k)
#define mst(a,b) memset(a,b,sizeof(a))
#define cout3(x,y,z) cout<<x<<" "<<y<<" "<<z<<endl
#define cout2(x,y) cout<<x<<" "<<y<<endl
#define cout1(x) cout<<x<<endl
#define O2 #pragma GCC optimize(2)
#define IOS std::ios::sync_with_stdio(false)
#define SRAND srand((unsigned int)(time(0)))
typedef long long ll;
typedef unsigned long long ull;
typedef unsigned int uint;
using namespace std;
const double PI=acos(-1.0);
const int INF=0x3f3f3f3f;
const ll mod=1e9+7;
const double eps=1e-8;
const int maxn=100005;
const int maxm=500005;
int fac(int l,int r,int x){
return r/x-(l-1)/x;
}
void solve() {
int l1,r1,l2,r2;
while(~scanf("%d%d%d%d",&l1,&r1,&l2,&r2)){
ll ans=0;
ans+=(ll)fac(l1,r1,2018)*(r2-l2+1);
ans+=(ll)fac(l2,r2,2018)*(r1-l1+1);
ans-=(ll)fac(l1,r1,2018)*fac(l2,r2,2018);
ans+=(ll)(fac(l1,r1,1009)-fac(l1,r1,2018))*(fac(l2,r2,2)-fac(l2,r2,2018));
ans+=(ll)(fac(l2,r2,1009)-fac(l2,r2,2018))*(fac(l1,r1,2)-fac(l1,r1,2018));
printf("%lld\n",ans);
}
return ;
}
int main() {
#ifdef LOCAL
freopen("in.txt","r",stdin);
// freopen("out.txt","w",stdout);
#else
// freopen("","r",stdin);
// freopen("","w",stdout);
#endif
solve();
return 0;
}