D - Circle Lattice Points

#include<bits/stdc++.h>
#define Woody
#define int long long
#define lowbit(x) (x&-x)
#define rep(n) for(int i=0;i<n;i++)
#define mp make_pair
#define eb emplace_back
#define F first
#define S second
#define SZ(a) (int)(a.size())
#define all(v) v.begin(),v.end()
#define SETIO(s) ifstream cin(s+".in");ofstream cout(s+".out");
#ifdef Woody
#define quick ios::sync_with_stdio(0);cin.tie(0);
#else
#define quick
#endif
#define INF INT64_MAX
using namespace std;
typedef pair<int,int> pii;
int x,y,Range;
bool ok(int px,int py){
    return px*px<=Range*Range-py*py;
}
signed main(){
    quick
    double a,b,c;
    cin>>a>>b>>c;
    x=a*10000;
    y=b*10000;
    Range=c*10000;
    int uy=(y+Range)/10000*10000+10000;
    int dy=(y-Range)/10000*10000-10000;
    int Minx=(x-Range)/10000*10000-10000;
    int Maxx=(x+Range)/10000*10000+10000;
    int ans=0;
    int lx;
    int rx;
    for(int i=uy;i>=dy;i-=10000){
        if(!ok(0,i-y)) continue;
        int l=Minx;
        int r=x;
        while(l+1<r){
            int middle=(l+r)>>1;
            if(ok(middle-x,i-y)) r=middle;
            else l=middle;
        }
        lx=r;
        l=x;
        r=Maxx;
        while(l+1<r){
            int middle=(l+r)>>1;
            if(ok(middle-x,i-y)) l=middle;
            else r=middle;
        }
        rx=l;
//      cout<<i<<":"<<lx<<" "<<rx<<"\n";
        int R;
        int L;
        if(rx>=0){
            R=rx/10000;
        }
        else {
            R=(rx/10000-(rx%10000!=0));
        }
        if(lx>=0){
            L=lx/10000+(lx%10000!=0);
        }
        else {
            L=(lx/10000);
        }
        ans+=R-L+1;
    }
    cout<<ans<<"\n";
}