using System;
using System.Collections.Generic;
public class Program {
  public static void Main()
    {
        string line = System.Console.ReadLine();
        string[] po = line.Split();
        int n = int.Parse(po[0]), m = int.Parse(po[1]), k = int.Parse(po[2]), current = 0, score = 0;
        List<int> mapK = new List<int>();
        Char[,] map = new Char[n, m];
        for (int i = 0; i < n; i++)
        {
            line = System.Console.ReadLine();
            for (int j = 0; j < m; j++)
            {
                map[i, j] = line[j];
            }
        }

        int w = 0;
           for (int i = 0; i < m; i++)
        {
            w = 0;
            for (int j = 0; j < n; j++)
            {
                if (map[j, i] == 'o')
                {
                    w++;
                }
                else
                {
                    mapK.Add(w);
                    w = 0;
                }
            }
            mapK.Add(w);
           
        }

        mapK.Sort();
        mapK.Reverse();
        for (int i = 0; i < mapK.Count; i++)
        {
            if (k < 2) break;

            current = System.Math.Min(mapK[i], k);
            score += current - 1;
            k -= current;
        }

        System.Console.WriteLine(score);
    }
}