#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<set>
#include<map>
#include<vector>
#include<queue>
using namespace std;
#define ll long long
#define RG register
#define MAX 1111
inline int read()
{
    RG int x=0,t=1;RG char ch=getchar();
    while((ch<'0'||ch>'9')&&ch!='-')ch=getchar();
    if(ch=='-')t=-1,ch=getchar();
    while(ch<='9'&&ch>='0')x=x*10+ch-48,ch=getchar();
    return x*t;
}
struct BigInt
{
	int s[20000],ws;
	void init(){s[1]=1;ws=1;}
	void Multi(int x)
	{
		for(int i=1;i<=ws;++i)s[i]=s[i]*x;
		for(int i=1;i<=ws;++i)s[i+1]+=s[i]/10,s[i]%=10;
		while(s[ws+1])++ws,s[ws+1]=s[ws]/10,s[ws]%=10;
	}
	void output(){for(int i=ws;i;--i)printf("%d",s[i]);}
}Ans1,Ans2;
int pri[20001],tot;
bool zs[20001];
void getpri()
{
	zs[1]=true;
	for(int i=2;i<=20000;++i)
	{
		if(!zs[i])pri[++tot]=i;
		for(int j=1;j<=tot&&i*pri[j]<=20000;++j)
		{
			zs[i*pri[j]]=true;
			if(i%pri[j]==0)break;
		}
	}
}
int Mul[20001],Div[20001];
int sum,a[MAX];
int n,m,D;
void Calc(int x,int *f)
{
	for(int i=1;i<=tot;++i)
		while(x%pri[i]==0)
		{
			f[pri[i]]++;
			x/=pri[i];
		}
}
int main()
{
	n=read();m=read();D=read();
	for(int i=1;i<=n;++i)a[i]=read(),sum+=a[i];
	getpri();
	for(int i=1;i<=m;++i)
	{
		int x=read(),y=read();
		if(!a[y]){puts("0/1");return 0;}
		Calc(a[y],Mul);Calc(sum,Div);
		a[y]+=D;sum+=D;
	}
	for(int i=1;i<=20000;++i)
		if(Div[i]>=Mul[i])Div[i]-=Mul[i],Mul[i]=0;
		else Mul[i]-=Div[i],Div[i]=0;
	Ans1.init();Ans2.init();
	for(int i=1;i<=20000;++i)
		for(int j=1;j<=Mul[i];++j)Ans1.Multi(i);
	for(int i=1;i<=20000;++i)
		for(int j=1;j<=Div[i];++j)Ans2.Multi(i);
	Ans1.output();putchar('/');Ans2.output();puts("");
	return 0;
}