#include <iostream>
#include <algorithm>
#include <vector>
#include <cmath>
#include <map>
#include <numeric>

typedef long long ll;

ll stringToFixedPoint(const std::string s, const int digitAfterDecimalPoint)
{
    ll fp = std::stoi(s) * pow(10, digitAfterDecimalPoint);
    const auto pos = s.find('.');
    if (pos != std::string::npos) {
        std::string afterDecimalPoint = s.substr(pos + 1);
        fp += std::stoi(afterDecimalPoint) * pow(10, digitAfterDecimalPoint - afterDecimalPoint.length());
    }

    return fp;
}


int main(int argc, char *argv[])
{
    std::string strX, strY, strR;

    std::cin >> strX >> strY >> strR;

    ll cx, cy, cr;
    const int digitAfterDecimalPoint = 4;
    const ll k = pow(10, digitAfterDecimalPoint);
    cx = stringToFixedPoint(strX, digitAfterDecimalPoint);
    cy = stringToFixedPoint(strY, digitAfterDecimalPoint);
    cr = stringToFixedPoint(strR, digitAfterDecimalPoint);

    ll ans = 0;
    for (ll y = (((cy + cr) / k) * k); y >= cy - cr; y -= k) {
        ll dy = y - cy;
        ll dxp = sqrt(cr * cr - dy * dy) + k;

        bool xmaxFound = false;
        ll xmax;
        for (ll x = (((cx + dxp) / k) * k); x >= cx - dxp; x -= k) {
            ll dx = x - cx;
            ll r2 = dy * dy + dx * dx;
            if (r2 <= cr * cr) {
                xmaxFound= true;
                xmax = x;
                break;
            }
        }
        if (!xmaxFound) {continue;}
        ll xmin;
        for (ll x = (((cx - dxp) / k) * k); x <= cx + dxp; x += k) {
            ll dx = x - cx;
            ll r2 = dy * dy + dx * dx;
            if (r2 <= cr * cr) {
                xmin = x;
                break;
            }
        }
        ll ansAdd = (xmax - xmin) / k + 1;
        ans += ansAdd;
    }

    std::cout << ans << std::endl;

    return 0;
}

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

int main() {
	long long N, K, M, COUNT = 0, A;
	cin >> N >> K >> M;
	COUNT = N * M;
	for (int i = 0; i < N - 1; i++) cin >> A, COUNT -= A;
	cout << (COUNT > K ? -1 : max(0LL, COUNT)) << endl;
}