View Compilation Error

0_0_17338142_25915.cpp: In function 'void getsa()':
0_0_17338142_25915.cpp:22:54: error: 'sqrt' was not declared in this scope
   distan = sqrt((x - x1)*(x - x1) + (y - y1)*(y - y1));
                                                      ^
0_0_17338142_25915.cpp: In function 'double getint(int, int)':
0_0_17338142_25915.cpp:32:17: error: 'sqrt' was not declared in this scope
  dis += x*sqrt(2);
                 ^