Main.cc: In function ‘int main()’:
Main.cc:21:32: error: expected ‘;’ before ‘]’ token
if(a[i][j-1]=='.') a[i][j-1]]='!';
^
Main.cc:21:31: warning: statement has no effect [-Wunused-value]
if(a[i][j-1]=='.') a[i][j-1]]='!';
~~~~~~~~^