View Compilation Error

0_0_28489038_10224.cpp: In function 'int calc()':
0_0_28489038_10224.cpp:21:18: error: 'n' was not declared in this scope
   for(int i=1;i<=n;i++) 
                  ^
0_0_28489038_10224.cpp: In function 'int main()':
0_0_28489038_10224.cpp:37:24: error: 'scanf' was not declared in this scope
     while(scanf("%d",&n)!=EOF){
                        ^
0_0_28489038_10224.cpp:37:27: error: 'EOF' was not declared in this scope
     while(scanf("%d",&n)!=EOF){
                           ^
0_0_28489038_10224.cpp:41:18: error: 'printf' was not declared in this scope
         printf("")
                  ^