这是小学数学题吧？？

#include <iostream>

using namespace std;

int n, n1, p1, n2, p2, n3, p3;

int main(void) {
  cin >> n >> n1 >> p1 >> n2 >> p2 >> n3 >> p3;

  int num = 0, cost1 = 0;
  while (num < n) {
    cost1 += p1;
    num += n1;
  }

  num = 0; int cost2 = 0;
  while (num < n) {
    cost2 += p2;
    num += n2;
  }

  num = 0; int cost3 = 0;
  while (num < n) {
    cost3 += p3;
    num += n3;
  }

  cout << min(cost1, min(cost2, cost3)) << endl;
  return 0;
}