View Compilation Error

0_0_37805332_11478.cpp: In instantiation of 'T read() [with T = int]':
0_0_37805332_11478.cpp:120:20:   required from here
0_0_37805332_11478.cpp:18:21: error: 'sum' cannot be used as a function
   sum = sum(sum << 1) + (sum << 3) + (ch ^ 48);
                     ^
0_0_37805332_11478.cpp: In instantiation of 'void read(T&) [with T = int]':
0_0_37805332_11478.cpp:42:8:   required from 'void read(T&, Args& ...) [with T = int; Args = {int}]'
0_0_37805332_11478.cpp:72:11:   required from here
0_0_37805332_11478.cpp:35:21: error: expression cannot be used as a function
   sum = sum(sum << 1) + (sum << 3) + (ch ^ 48);
                     ^