View Compilation Error

0_0_14259813_4422.cpp: In function 'int main()':
0_0_14259813_4422.cpp:17:47: error: 'memset' was not declared in this scope
 #define clr(vis, a) memset(vis, a, sizeof(vis))
                                               ^
0_0_14259813_4422.cpp:42:9: note: in expansion of macro 'clr'
         clr(vis, 0);
         ^