View Compilation Error

0_0_37442366_26998.cpp: In function 'int comp(int)':
0_0_37442366_26998.cpp:10:19: error: 'sqrt' was not declared in this scope
 for (i=2;i<=sqrt(n);i++)
                   ^
0_0_37442366_26998.cpp: In function 'int main()':
0_0_37442366_26998.cpp:48:25: error: 'memset' was not declared in this scope
 memset(vis,0,sizeof(vis));
                         ^