C++ combination program problem

I would want to write a C++ program to show combination..but I cant do it.May anyone help me to check my program and teach me to correct it ?? My goal id to input the n and k then it will show the combination to me. #include <iostream> using namespace std; int main() { int n,answer; int j=1; cout << "Input n and k :"<<endl; cin >> n,k; answer=(n - j + 1) / j ; while(j<=k){ answer= answer *(n - j + 1) / j ; ++j ; } cout<<"The number of combinations is :"<< answer << endl; system("PAUSE"); return 0; }