View Compilation Error

0_0_27771891_19984.cpp:11:25: error: 'rt' has not been declared
 void build(int l,int r, rt){
                         ^
0_0_27771891_19984.cpp: In function 'void build(int, int, int)':
0_0_27771891_19984.cpp:14:25: error: 'rt' was not declared in this scope
         scanf("%d",&sum[rt]);
                         ^
0_0_27771891_19984.cpp:3:18: error: 'rt' was not declared in this scope
 #define lson l,m,rt<<1
                  ^
0_0_27771891_19984.cpp:18:11: note: in expansion of macro 'lson'
     build(lson);
           ^