View Compilation Error

0_0_13927753_23205.cpp: In function 'int main()':
0_0_13927753_23205.cpp:31:27: error: lvalue required as decrement operand
  while(!isdigit(*(end-1)) --end;
                           ^
0_0_13927753_23205.cpp:31:29: error: expected ')' before 'end'
  while(!isdigit(*(end-1)) --end;
                             ^