foo.cpp: In function 'int main()':
foo.cpp:11:26: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
     while ( ch = getchar() )
                          ^
foo.cpp:49:34: error: 'abs' was not declared in this scope
             while ( abs(cnt1-cnt2) == 2 )
                                  ^
foo.cpp:57:31: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
         if ( flag==0&&i!=len-1&&cnt1==11||cnt2==11 )
                               ^
foo.cpp:62:42: error: 'abs' was not declared in this scope
         else if ( flag==1&&(abs(cnt1-cnt2)==2) )
                                          ^
foo.cpp:88:22: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
         if ( i!=len-1&&cnt1==21||cnt2==21 )
                      ^