View Compilation Error

0_0_29978802_30251.cpp: In function 'void build(int, int, int)':
0_0_29978802_30251.cpp:13:11: error: 'lson' was not declared in this scope
     build(lson,l,(l+r)/2);
           ^
0_0_29978802_30251.cpp:14:11: error: 'rson' was not declared in this scope
     build(rson,(l+r)/2+1,r);
           ^