View Compilation Error

0_0_37679286_17127.cpp: In function 'int main()':
0_0_37679286_17127.cpp:61:61: error: 'gcd' was not declared in this scope
                             lcm = lcm * v[j] / gcd(lcm, v[j]);
                                                             ^
0_0_37679286_17127.cpp:71:46: error: 'gcd' was not declared in this scope
                         if (gcd(pr.first, tmp) == 1)
                                              ^
0_0_37679286_17127.cpp:73:47: error: 'gcd' was not declared in this scope
                         if (gcd(pr.second, tmp) == 1)
                                               ^