Codeforces Round #184 (Div. 2)

A. Strange Addition

#include<cmath>
#include<cstdio>
#include<vector>
#include<cstring>
#include<iostream>
#include<algorithm>

using namespace std;
typedef long long ll;

int main()
{
ll p , q , a;
int n , flag = 0;
cin>>p>>q>>n;
//    cout<<p<<q<<endl;
for(int i = 0;i < n;i ++)
{
cin>>a;
if(q <= 0 || a > ( p/q ))//当q 为0要跳出循环
{
flag = 1;
break;
}
p = p - a * q;    //  乘p 模拟
//    cout<<p<<endl;
swap(p,q);
}
if(flag != 1)
{
if(q == 0)
printf("YES\n");
else
printf("NO\n");
}
else
printf("NO\n");
return 0;
}