#include <bits/stdc++.h>
#define int long long
#define lc p<<1
#define rc p<<1|1
#define pb push_back
#define pii pair<int,int>
#define st first
#define nd second
using namespace std;
inline int read(){
    int x=0,f=1;char ch=getchar();
    for(;!isdigit(ch);ch=getchar())f^=ch=='-';
    for(;isdigit(ch);ch=getchar())x=x*10+(ch^48);
    return f?x:-x;
}
mt19937 rnd(time(0));
const int mo=998244353;
inline int qpow(int x,int t){
    int ret=1;
    for(;t;t>>=1,x=x*x%mo)if(t&1)ret=ret*x%mo;
    return ret;
}
inline void red(int &x){x>=mo?x-=mo:0;}
inline void chmin(int &x,int y){x=min(x,y);}
inline void chmax(int &x,int y){x=max(x,y);}
const int N=1005;
char str[N][N],ff[N][N];
int n,m,tag[N][N],qd[N][N];
struct oper{
    int x,y,dx,dy;
    char c;
    pii type,ori;
};
vector<oper> op;
pii rev(pii t,int x,int y){
    if(t.st==-1)t.st=x;
    if(t.nd==-1)t.nd=y;
    return t;
}
void output(int t=0){
    for(int i=1;i<=n;++i,puts(""))for(int j=1;j<=m;++j){
        if(!ff[i][j])putchar('.');
        else putchar(ff[i][j]);
    }
    if(t==1){
        for(int i=1;i<=n;++i,puts(""))for(int j=1;j<=m;++j){
            printf("%lld ",qd[i][j]);
        }
    }
    if(t==2){
        for(int i=0;i<=n+1;++i,puts(""))for(int j=0;j<=m+1;++j){
            printf("%lld ",tag[i][j]);
        }
    }
}
int in(int x,int l,int r){return l<=x&&x<=r;}
void work(int i1,int i2,int j1,int j2){
    // printf("This is the :(%lld,%lld,%lld,%lld) work\n",i1,i2,j1,j2);
    if(i1>i2)return;
    if(j1>j2)return;
    op.clear();
    if(!tag[i1][0])op.pb(oper{i1,j1,0,1,str[i1][0],{0,-1},{i1,0}});
    if(!tag[i1][m+1])op.pb(oper{i1,j2,0,-1,str[i1][m+1],{0,-1},{i1,m+1}});
    if(!tag[i2][0])op.pb(oper{i2,j1,0,1,str[i2][0],{n+1,-1},{i2,0}});
    if(!tag[i2][m+1])op.pb(oper{i2,j2,0,-1,str[i2][m+1],{n+1,-1},{i2,m+1}});
    if(!tag[0][j1])op.pb(oper{i1,j1,1,0,str[0][j1],{-1,0},{0,j1}});
    if(!tag[n+1][j1])op.pb(oper{i2,j1,-1,0,str[n+1][j1],{-1,0},{n+1,j1}});
    if(!tag[0][j2])op.pb(oper{i1,j2,1,0,str[0][j2],{-1,m+1},{0,j2}});
    if(!tag[n+1][j2])op.pb(oper{i2,j2,-1,0,str[n+1][j2],{-1,m+1},{n+1,j2}});
    //recheck : so try again
    if(!tag[i1][0])op.pb(oper{i1,j1,0,1,str[i1][0],{0,-1},{i1,0}});
    if(!tag[i1][m+1])op.pb(oper{i1,j2,0,-1,str[i1][m+1],{0,-1},{i1,m+1}});
    if(!tag[i2][0])op.pb(oper{i2,j1,0,1,str[i2][0],{n+1,-1},{i2,0}});
    if(!tag[i2][m+1])op.pb(oper{i2,j2,0,-1,str[i2][m+1],{n+1,-1},{i2,m+1}});
    if(!tag[0][j1])op.pb(oper{i1,j1,1,0,str[0][j1],{-1,0},{0,j1}});
    if(!tag[n+1][j1])op.pb(oper{i2,j1,-1,0,str[n+1][j1],{-1,0},{n+1,j1}});
    if(!tag[0][j2])op.pb(oper{i1,j2,1,0,str[0][j2],{-1,m+1},{0,j2}});
    if(!tag[n+1][j2])op.pb(oper{i2,j2,-1,0,str[n+1][j2],{-1,m+1},{n+1,j2}});
    for(oper T:op){
        int x=T.x,y=T.y,dx=T.dx,dy=T.dy;
        char c=T.c;
        pii pos=T.type;
        int r=0;
        while(in(x,i1,i2)&&in(y,j1,j2)){
            if(ff[x][y]){
                if(ff[x][y]==c)r=1;
                break;
            }
            else{
                pii tmp=rev(pos,x,y);
                if(tag[tmp.st][tmp.nd]){
                    ff[x][y]=c;
                    r=1;
                    break;
                }
                qd[x][y]=-1;
                x+=dx;
                y+=dy;
            }
        }
        if(!r)return;
        else tag[T.ori.st][T.ori.nd]=1;
    }
    // puts("First Work");
    // output(1);

    for(int i=i1+1;i<i2;++i){
        if(qd[i][j1]!=-1){
            if(ff[i][j1]){
                tag[i][0]|=(ff[i][j1]==str[i][0]);
            }
            else{
                if(!tag[i][0]){
                    ff[i][j1]=str[i][0];
                    tag[i][0]=1;
                }
            }
        }
    }
    for(int i=i1+1;i<i2;++i){
        if(qd[i][j2]!=-1){
            if(ff[i][j2]){
                tag[i][m+1]|=(ff[i][j2]==str[i][m+1]);
            }
            else{
                if(!tag[i][m+1]){
                    ff[i][j2]=str[i][m+1];
                    tag[i][m+1]=1;
                }
            }
        }
    }
    for(int j=j1+1;j<j2;++j){
        if(qd[i1][j]!=-1){
            if(ff[i1][j]){
                tag[0][j]|=(ff[i1][j]==str[0][j]);
            }
            else{
                if(!tag[0][j]){
                    ff[i1][j]=str[0][j];
                    tag[0][j]=1;
                }
            }
        }
    }
    for(int j=j1+1;j<j2;++j){
        if(qd[i2][j]!=-1){
            if(ff[i2][j]){
                tag[n+1][j]|=(ff[i2][j]==str[n+1][j]);
            }
            else{
                if(!tag[n+1][j]){
                    ff[i2][j]=str[n+1][j];
                    tag[n+1][j]=1;
                }
            }
        }
    }
    // puts("Second work");
    // output(2);
    work(i1+1,i2-1,j1+1,j2-1);
}
void solve(){
    n=read(),m=read();
    for(int i=0;i<=n+1;++i)scanf("%s",str[i]);
    for(int i=1;i<=n;++i){
        if(str[i][0]=='.')tag[i][0]=1;
        if(str[i][m+1]=='.')tag[i][m+1]=1;
    }
    for(int j=1;j<=m;++j){
        if(str[0][j]=='.')tag[0][j]=1;
        if(str[n+1][j]=='.')tag[n+1][j]=1;
    }
    for(int i=1;i<=n;++i)for(int j=1;j<=m;++j){
        if(str[i][j]=='x')ff[i][j]='.';
    }
    work(1,n,1,m);
    for(int i=1;i<=n;++i){
        if(!tag[i][0]){
            puts("NO");
            return;
        }
        if(!tag[i][m+1]){
            puts("NO");
            return;
        }
    }
    for(int j=1;j<=m;++j){
        if(!tag[0][j]){
            puts("NO");
            return;
        }
        if(!tag[n+1][j]){
            puts("NO");
            return;
        }
    }
    for(int i=1;i<=n;++i,puts(""))for(int j=1;j<=m;++j){
        if(!ff[i][j])putchar('.');
        else putchar(ff[i][j]);
    }
    return;
}
signed main(){
    // freopen("D.out","w",stdout);
    for(int cas=1;cas--;)solve();
    return 0;
}