#include <stdio.h>#include <string.h>#include <algorithm>using namespace std;char str[55][25],tmp[55][25],ans[27];int n,flag;int judge(int x,int y,char ch){ int j; for (j=x;j<n;j++) { if (str[j][y]>='A'&&str[j][y]<='Z'&&str[j][y]!=ch) { flag=1;return 1; } } return 0;}void dfs(int x,int y,char ch){ int i,j,row,col,dir[4][2]={-1,0,1,0,0,-1,0,1}; for (i=0;i<4;i++) { row=dir[i][0]+x; col=dir[i][1]+y; if (row<n&&col<20&&row>=0&&col>=0&&tmp[row][col]==ch) { if(judge(row,col,ch))return; tmp[row][col]='.'; dfs(row,col,ch); if(flag)tmp[row][col]=ch; } }}void slove1(){ int i,j,k=0; for (j=0;j<20;j++) { for (i=n-1;i>=0;i--) { flag=0; if (tmp[i][j]!='.') { tmp[i][j]='.'; if(!judge(i,j,str[i][j])) dfs(i,j,str[i][j]); if(flag)tmp[i][j]=str[i][j]; else ans[k++]=str[i][j]; break; } } } sort(ans,ans+k); printf("%c",ans[0]);}void slove2(){ int i,j; for (j=0;j<20;j++) { for (i=n-1;i>=0;i--) { if (tmp[i][j]==ans[0]) { tmp[i][j]='.'; dfs(i,j,ans[0]); return; } } }}void Copy1(){ int i; for (i=0;i<n;i++)strcpy(tmp[i],str[i]);}void Copy2(){ int i; for (i=0;i<n;i++)strcpy(str[i],tmp[i]);}int main(){ int i,j,num=0,vis[27]={0}; scanf("%d",&n); for (i=0;i<n;i++) { scanf("%s",str[i]); strcpy(tmp[i],str[i]); for(j=0;j<20;j++) { if(str[i][j]!='.'&&!vis[str[i][j]-'A']) { vis[str[i][j]-'A']=1; num++; } } } for (i=0;i<num;i++) { slove1(); Copy1(); slove2(); Copy2(); } printf("n"); return 0;}
