C++ :

#include<bits/stdc++.h>
using namespace std;
typedef pair<int,int> PII;
#define x first
#define y second
const int N=110;
int dist[N][N];
char g[N][N];
int n,m;
int sx,sy;
int dx[]={-1,-1,-1,0,0,1,1,1};
int dy[]={-1,0,1,-1,1,-1,0,1};
void bfs()
{
    memset(dist,0x3f,sizeof dist);
    queue<PII> q;
    q.push({sx,sy});
    dist[sx][sy]=0;
    while(q.size())
    {
        PII t=q.front();
        q.pop();
        for(int i=0;i<8;i++)
        {
            int a=t.x+dx[i],b=t.y+dy[i];
            if(a<=0||a>n||b<=0||b>m) continue;
            if(g[a][b]=='*') continue;
            if(dist[a][b]!=0x3f3f3f3f) continue;
            dist[a][b]=dist[t.x][t.y]+1;
            q.push({a,b});
        }
    }
}
int main()
{
    cin>>m>>n>>sy>>sx;
    for(int i=1;i<=n;i++) cin>>g[i]+1;
    sx=n+1-sx;
    bfs();
    int res=0;
    for(int i=1;i<=n;i++)
    {
        for(int j=1;j<=m;j++)
        {
            if(g[i][j]!='*')
            {
                res=max(res,dist[i][j]);
            }
        }
    }
    cout<<res;
    return 0;
}