View Compilation Error

0_0_20677423_7794.cpp: In function 'int main()':
0_0_20677423_7794.cpp:4:17: error: 'scanf' was not declared in this scope
   scanf("%d" ,&t); 
                 ^
0_0_20677423_7794.cpp:7:5: error: 'intn' was not declared in this scope
     intn;
     ^
0_0_20677423_7794.cpp:8:17: error: 'n' was not declared in this scope
     scanf("%d",&n); 
                 ^
0_0_20677423_7794.cpp:9:34: error: 'printf' was not declared in this scope
     printf("Case#%d:%d\n",T,2*n-1) ; 
                                  ^