View Compilation Error

0_0_33300223_3365.cpp:6:28: error: conflicting declaration 'int M'
 int L,R,n,T[U<<2],v[N],x,y,M,ans;
                            ^
0_0_33300223_3365.cpp:5:28: note: previous declaration as 'const int M'
 const int U=50000,N=500005,M=65536;
                            ^