View Compilation Error

0_0_9496411_31098.cpp: In function `long long int lcm(long long int, long long int)':
0_0_9496411_31098.cpp:9: error: `gcd' undeclared (first use this function)
0_0_9496411_31098.cpp:9: error: (Each undeclared identifier is reported only once for each function it appears in.)