View Compilation Error

0_0_32850345_6806.cpp: In function 'int main()':
0_0_32850345_6806.cpp:7:30: error: 'scanf' was not declared in this scope
     while (scanf("%d%d",&n,&m)!=EOF)
                              ^
0_0_32850345_6806.cpp:7:33: error: 'EOF' was not declared in this scope
     while (scanf("%d%d",&n,&m)!=EOF)
                                 ^
0_0_32850345_6806.cpp:43:22: error: 'puts' was not declared in this scope
             puts("-1");
                      ^
0_0_32850345_6806.cpp:50:30: error: 'printf' was not declared in this scope
             printf("%d\n",sum);
                              ^