百度之星-百度的新大厦

#include <iostream>
using namespace std;


const int MAXN = 100000000;


int main()
{
long long ciShu, dianTi;
cin >> ciShu >> dianTi;
long long ans = MAXN;
for (int i = 0; i < dianTi; i++)
{
long long ui, di;
cin >> ui >> di;
long long uu = (ui*ciShu -1)/(ui+di);
long long dd = ciShu - uu;
int suoZai = ui*dd - di*uu;
if (ans >= suoZai)
{
ans = suoZai;
}
}
cout << ans << endl;
// system("pause");
return 0;
}