View Compilation Error

0_0_9877085_7195.cpp: In function `int main()':
0_0_9877085_7195.cpp:11: error: `gcd' undeclared (first use this function)
0_0_9877085_7195.cpp:11: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_9877085_7195.cpp: In function `int gcd(int, int)':
0_0_9877085_7195.cpp:18: error: `int gcd(int, int)' used prior to declaration