/in/foo.cc: In function 'int main()':
/in/foo.cc:57:44: warning: array subscript has type 'char' [-Wchar-subscripts]
    if(a[i][min_y]!=ch&&temp_vis[a[i][min_y]]){
                                            ^
/in/foo.cc:60:25: warning: array subscript has type 'char' [-Wchar-subscripts]
     temp_vis[a[i][min_y]]=false;
                         ^
/in/foo.cc:62:44: warning: array subscript has type 'char' [-Wchar-subscripts]
    if(a[i][max_y]!=ch&&temp_vis[a[i][max_y]]){
                                            ^
/in/foo.cc:65:25: warning: array subscript has type 'char' [-Wchar-subscripts]
     temp_vis[a[i][max_y]]=false;  
                         ^
/in/foo.cc:69:44: warning: array subscript has type 'char' [-Wchar-subscripts]
    if(a[min_x][i]!=ch&&temp_vis[a[min_x][i]]){
                                            ^
/in/foo.cc:72:25: warning: array subscript has type 'char' [-Wchar-subscripts]
     temp_vis[a[min_x][i]]=false;
                         ^
/in/foo.cc:74:44: warning: array subscript has type 'char' [-Wchar-subscripts]
    if(a[max_x][i]!=ch&&temp_vis[a[max_x][i]]){
                                            ^
/in/foo.cc:77:25: warning: array subscript has type 'char' [-Wchar-subscripts]
     temp_vis[a[max_x][i]]=false;
                         ^