View Compilation Error

0_0_16310994_22791.cpp: In function 'int main()':
0_0_16310994_22791.cpp:5:36: error: 'memset' was not declared in this scope
 #define clr(p) memset(p,0,sizeof(p))
                                    ^
0_0_16310994_22791.cpp:48:24: note: in expansion of macro 'clr'
     for(c=1;c<=CS;++c){clr(a);clr(dis);clr(gap);ans=0;
                        ^