P3717 [AHOI2017初中组]cover

#include <iostream>    
using namespace std;   
int main()               
{                     
    bool map[201][201];
    int a,b,n,m,r,s=0;
    cin >> n >> m >> r;
    for(int i=1;i <= m;i++)
    {
        cin >> a >> b;
        for(int x=a-r;x <= a+r;x++)
        for(int y=b-r;y <= b+r;y++)
        if(x >= 1 && x <= n && y >= 1 && y <= n)
        if(map[x][y] == false && (a-x)*(a-x)+(b-y)*(b-y) <= r*r)
        map[x][y]=true,s++;
    }
    cout << s;
    return 0;
}