View Compilation Error

0_0_24860659_12151.cpp: In function 'int main()':
0_0_24860659_12151.cpp:5:29: error: 'scanf' was not declared in this scope
     while(scanf("%d%d",&x,&y)==2){
                             ^
0_0_24860659_12151.cpp:6:26: error: 'puts' was not declared in this scope
         if(x>y){puts("-1");continue;}
                          ^
0_0_24860659_12151.cpp:7:41: error: 'printf' was not declared in this scope
         if(x==1||x==y){printf("%d\n",y-1);continue;}
                                         ^
0_0_24860659_12151.cpp:20:26: error: 'printf' was not declared in this scope
         printf("%d\n",ans);
                          ^