View Compilation Error

0_0_9051688_18687.cpp:5: error: `_int64' does not name a type
0_0_9051688_18687.cpp: In function `int main()':
0_0_9051688_18687.cpp:24: error: `gcd' undeclared (first use this function)
0_0_9051688_18687.cpp:24: error: (Each undeclared identifier is reported only once for each function it appears in.)