View Compilation Error

0_0_19741515_1525.cpp: In function 'void gn(int&)':
0_0_19741515_1525.cpp:2:29: error: 'getchar' was not declared in this scope
     char c;while((c=getchar())<'0'||c>'9');x=c-'0';
                             ^
0_0_19741515_1525.cpp:3:22: error: 'getchar' was not declared in this scope
     while((c=getchar())>='0'&&c<='9')x=x*10+c-'0';
                      ^