View Compilation Error

0_0_33274226_4836.cpp: In function 'int main()':
0_0_33274226_4836.cpp:10:21: error: 'scanf' was not declared in this scope
  while(scanf("%d",&N)!=EOF)
                     ^
0_0_33274226_4836.cpp:10:24: error: 'EOF' was not declared in this scope
  while(scanf("%d",&N)!=EOF)
                        ^
0_0_33274226_4836.cpp:16:35: error: 'sort' was not declared in this scope
   sort(soldierlevel,soldierlevel+N);//排序，让相同的士兵排在相邻位置 
                                   ^
0_0_33274226_4836.cpp:30:18: error: 'printf' was not declared in this scope
   printf("%d\n",s);
                  ^