View Compilation Error

0_0_31141893_31016.cpp: In function 'int main()':
0_0_31141893_31016.cpp:5:15: error: 'scanf' was not declared in this scope
  scanf("%d",&n);
               ^
0_0_31141893_31016.cpp:6:10: error: 'getchar' was not declared in this scope
  getchar();
          ^
0_0_31141893_31016.cpp:10:9: error: 'gets' was not declared in this scope
   gets(a);
         ^
0_0_31141893_31016.cpp:11:13: error: 'strlen' was not declared in this scope
   x=strlen(a)-1;
             ^
0_0_31141893_31016.cpp:19:17: error: 'printf' was not declared in this scope
   printf("yes\n");
                 ^
0_0_31141893_31016.cpp:21:16: error: 'printf' was not declared in this scope
   printf("no\n");
                ^