#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <numeric>
using namespace std;
int main()
{
    
    int N, A, X;
    while (cin >> N >> A >> X)
    {
        vector<int> arr(N, 0);
        for (int i = 0; i < N; ++i)
        {
            cin >> arr[i];
        }
        int minute = 60;
        int sum;
        int res;
        int acc = minute * A * X;
        sum = accumulate(arr.begin(), arr.end(), 0);
        int maxval = minute * (A * X + (8 - X));
        if (sum > maxval)
            cout << 0 << endl;
        if (sum <= acc)
        {
            res = ceil((float)sum / (float)A);
        }
        else
        {
            res = X * minute + (sum - acc);
        }
        cout << res << endl;    
    }
    return 0;
}
//8 2 8
//60 60 60 60 60 60 60 60
//4 3 3