View Compilation Error

0_0_24490307_8075.cpp: In function 'mat fast(mat, ll)':
0_0_24490307_8075.cpp:28:33: error: 'memset' was not declared in this scope
     memset(ans.m,0,sizeof(ans.m));
                                 ^
0_0_24490307_8075.cpp: In function 'int main()':
0_0_24490307_8075.cpp:49:33: error: 'memset' was not declared in this scope
         memset(a.m,0,sizeof(a.m));
                                 ^