View Compilation Error

0_0_20826432_7254.cpp: In function 'int main()':
0_0_20826432_7254.cpp:7:24: error: 'scanf' was not declared in this scope
     while(scanf("%d",&n)!=EOF)
                        ^
0_0_20826432_7254.cpp:7:27: error: 'EOF' was not declared in this scope
     while(scanf("%d",&n)!=EOF)
                           ^
0_0_20826432_7254.cpp:8:30: error: 'printf' was not declared in this scope
          printf("%d\n",a[n-1]);
                              ^