import std.array, std.stdio, std.string, std.algorithm, std.conv;


void main()
{
    auto v = readln.split.map!(to!long);
    int l = 0, u = 30000000;
    while (l < u) {
        int mid = (l + u + 1) / 2;
        int rem = 0, need = 0;
        foreach (i; v) {
            rem += max(i - mid, 0) / 2;
            need += max(mid - i, 0);
        }
        if (rem >= need) {
            l = mid;
        } else {
            u = mid - 1;
        }
    }
    writeln(u);
}