View Compilation Error

0_0_23335004_21787.cpp: In function 'int main()':
0_0_23335004_21787.cpp:15:27: error: 'scanf' was not declared in this scope
  while(scanf("%d %d",&n,&m)&&n!=-1&&m!=-1){
                           ^
0_0_23335004_21787.cpp:28:19: error: 'printf' was not declared in this scope
  printf("%.3f\n",c);}
                   ^