Gleb And Pizza CodeForces

 CodeForces - 842B 

#include<bits/stdc++.h>
using namespace std;

int main() {
    int r,d,t;
    double temp,x,y,z;
    while(~scanf("%d %d",&r,&d)) {
        scanf("%d",&t);
        int ans = 0;
        for(int i = 0; i < t; i++) {
            scanf("%lf %lf %lf",&x,&y,&z);
            temp = sqrt(x*x + y*y) - z ;
            if (temp >= (r-d) && temp + z + z <= r ) ans++;
         }
        cout<<ans<<endl;
    }
    return 0;
}