View Compilation Error

0_0_29044785_31121.cpp:7:1: error: 'ill' does not name a type
 ill gcd(ll x,ll y) ? //最大公约数?
 ^
0_0_29044785_31121.cpp:16:1: error: 'll' does not name a type
 ll lcm(ll x,ll y) ? ? ?//求最小公倍数
 ^
0_0_29044785_31121.cpp: In function 'int main()':
0_0_29044785_31121.cpp:35:15: error: 'gcd' was not declared in this scope
   x = gcd(a, b);
               ^
0_0_29044785_31121.cpp:49:34: error: 'lcm' was not declared in this scope
    printf("%lld/%lld\n", lcm(a, c), gcd(b, d));
                                  ^
0_0_29044785_31121.cpp:51:32: error: 'lcm' was not declared in this scope
   else printf("%lld\n",lcm(a, c));
                                ^