View Compilation Error

0_0_14684992_29478.cpp: In function 'bool input()':
0_0_14684992_29478.cpp:4:36: error: 'memset' was not declared in this scope
 #define clr(a) memset(a,0,sizeof(a))
                                    ^
0_0_14684992_29478.cpp:53:2: note: in expansion of macro 'clr'
  clr(tre);
  ^