/in/foo.cc: In function 'int main()':
/in/foo.cc:30:8: warning: unused variable 'flag' [-Wunused-variable]
    int flag=0;
        ^~~~
/in/foo.cc:41:18: warning: 'r' may be used uninitialized in this function [-Wmaybe-uninitialized]
     if((a[l]<=a[r+1] || r+1>n) && (a[r]>=a[l-1] || l-1<1)) printf("yes\n%d %d\n",l,r);
                 ~^~
/in/foo.cc:41:86: warning: 'l' may be used uninitialized in this function [-Wmaybe-uninitialized]
     if((a[l]<=a[r+1] || r+1>n) && (a[r]>=a[l-1] || l-1<1)) printf("yes\n%d %d\n",l,r);
                                                                                      ^