/in/foo.cc: In function 'int main()':
/in/foo.cc:27:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<strlen(a[0]);i++)
              ~^~~~~~~~~~~~~
/in/foo.cc:28:5: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses]
   if(a[0][i]=='?')
     ^
/in/foo.cc:43:7: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses]
     if(a[i+1][j]=='?')
       ^