foo.cpp: In function 'int main()':
foo.cpp:11:28: error: 'scanf' was not declared in this scope
     scanf("%d%d%d",&c,&m,&n);
                            ^
foo.cpp:14:26: error: 'printf' was not declared in this scope
             printf("%d",0);
                          ^
foo.cpp:25:26: error: 'printf' was not declared in this scope
             printf("%d",0);
                          ^
foo.cpp:34:24: error: 'printf' was not declared in this scope
     printf("%.3f",z/sum);
                        ^