初始值过小，没给它留缓冲空间
AC CODE:
```cpp
#include <cstdio>
#include <math.h>
#include <iostream>
using namespace std;
const int N=1e8+5;
int main(){
long int al = N,a,b,c,co;
cin >> c;
for (int i = 1;i < 4;i++){
cin >> a >>b;
if (a!=0){
co = ceil((float)c/a);
co *= b;}
// cout << c/a << endl;
if ((co<al)){
al = co;
}
}
cout << al;
}
```
by lan_chance @ 2023-11-22 20:53:50