View Compilation Error

0_0_18765268_27395.cpp: In function 'int main()':
0_0_18765268_27395.cpp:6:18: error: 'scanf' was not declared in this scope
     scanf("%d",&t);
                  ^
0_0_18765268_27395.cpp:11:21: error: 'strlen' was not declared in this scope
         n=strlen(s+1);
                     ^
0_0_18765268_27395.cpp:20:25: error: 'printf' was not declared in this scope
         printf("d\n",ans);
                         ^