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

int main(){
    long double x,y,r; cin>>x>>y>>r; r = nextafter(r,INFINITY);
    ll ans=0;

    for(ll i=ceil(x-r);i<=floor(x+r);i++){
        long double p = sqrt(pow(r,2) - pow(i-x,2));
        ans += floor(y+p) - ceil(y-p) + 1;
    }
    cout << ans << endl;
}
#include <bits/stdc++.h>
#ifdef LILY
#include "./DebugOutput.h"
#else
#define dbg(...) (0)
#endif
using int32 = int;
using int64 = long long;
using namespace std;

class Solution
{
#define int int64
#define sfor(i, n) for (int i = 1; i <= n; ++i)
#define tfor(i, n) for (int i = 0; i < n; ++i)

    int x, y, r, res = 0;

    void SHURU()
    {
        double a, b, c;
        cin >> a >> b >> c;
        x = round(a * 10000);
        y = round(b * 10000);
        r = round(c * 10000);
    }

    void SHUCHU()
    {
        cout << res << endl;
    }

    bool inCircle(int dx, int dy)
    {
        return dx * dx + dy * dy <= r * r;
    }

    void CHULI()
    {
        x %= 10000;
        y %= 10000;
        int l = 0, r = 1;
        for (int i = 1000100000; i >= 0; i -= 10000)
        {
            while (inCircle(x - l * 10000, y + i))
                --l;
            while (inCircle(x - r * 10000, y + i))
                ++r;
            res += r - l - 1;
        }
        l = 0;
        r = 1;
        for (int i = 1000100000; i >= 10000; i -= 10000)
        {
            while (inCircle(x - l * 10000, y - i))
                --l;
            while (inCircle(x - r * 10000, y - i))
                ++r;
            res += r - l - 1;
        }
        dbg(this->x, this->y, this->r);
    }

public:
    Solution()
    {
        SHURU();
        CHULI();
        SHUCHU();
    }
#undef int
#undef tfor
#undef sfor
};

int32 main()
{
#ifdef LILY
    while (1)
    {
#endif
        Solution();
#ifdef LILY
    }
#endif
    return 0;
}
