#include<bits/stdc++.h>
#define double long double

using namespace std;

const int MAXN=1e6+5;

namespace io {
	const int __SIZE = (1 << 21) + 1;
	char ibuf[__SIZE], *iS, *iT, obuf[__SIZE], *oS = obuf, *oT = oS + __SIZE - 1, __c, qu[55]; int __f, qr, _eof;
	#define Gc() (iS == iT ? (iT = (iS = ibuf) + fread (ibuf, 1, __SIZE, stdin), (iS == iT ? EOF : *iS ++)) : *iS ++)
	inline void flush () { fwrite (obuf, 1, oS - obuf, stdout), oS = obuf; }
	inline void gc (char &x) { x = Gc(); }
	inline void pc (char x) { *oS ++ = x; if (oS == oT) flush (); }
	inline void pstr (const char *s) { int __len = strlen(s); for (__f = 0; __f < __len; ++__f) pc (s[__f]); }
	inline void gstr (char *s) { for(__c = Gc(); __c < 32 || __c > 126 || __c == ' ';)  __c = Gc();
		for(; __c > 31 && __c < 127 && __c != ' ' && __c != '\n' && __c != '\r'; ++s, __c = Gc()) *s = __c; *s = 0; }
	template <class I> inline bool gi (I &x) { _eof = 0;
		for (__f = 1, __c = Gc(); (__c < '0' || __c > '9') && !_eof; __c = Gc()) { if (__c == '-') __f = -1; _eof |= __c == EOF; }
		for (x = 0; __c <= '9' && __c >= '0' && !_eof; __c = Gc()) x = x * 10 + (__c & 15), _eof |= __c == EOF; x *= __f; return !_eof; }
	template <class I> inline void print (I x) { if (!x) pc ('0'); if (x < 0) pc ('-'), x = -x;
		while (x) qu[++ qr] = x % 10 + '0',  x /= 10; while (qr) pc (qu[qr --]); }
	struct Flusher_ {~Flusher_(){flush();}}io_flusher_;
} using io::pc; using io::gc; using io::pstr; using io::gstr; using io::gi; using io::print;

int n;
long long x,p,q;
int a[MAXN];

signed main(){
	// double st=clock();
	// freopen("test.in","r",stdin);
	cin>>n>>x>>p>>q;
	for(int i=1;i<=n;++i) cin>>a[i];
	long long t=0;
	int indx=1;
	long long sum=0;
	double tmp=x*1.0*p/q;
	while(indx<=n){
		t++;
		int k=x-1;
		while(a[indx]<=k&&k>0&&indx<=n){
			k-=a[indx];
			++indx;
		}
		sum+=k+1;
		double tm=tmp*t;
		double kk=x;
		long long tt=ceil((tm-(double)sum)/(kk-tmp));
		if(tm>sum){
			t+=tt;
			sum+=tt*x;
		}
	}
	cout<<t<<endl;
	// double ed=clock();
	return 0;
}

样例都对了。SUB #2 和#5 各挂了一个点。

求助。

另外 为什么过了三个SUB只有三十啊（（（