View Compilation Error

262025_0_30875.cpp: In function `int main()':
262025_0_30875.cpp:4: error: `scanf' undeclared (first use this function)
262025_0_30875.cpp:4: error: (Each undeclared identifier is reported only once for each function it appears in.)
262025_0_30875.cpp:4: error: `EOF' undeclared (first use this function)
262025_0_30875.cpp:8: error: `getchar' undeclared (first use this function)
262025_0_30875.cpp:18: error: `gcd' undeclared (first use this function)
262025_0_30875.cpp:19: error: `printf' undeclared (first use this function)