// yukicoder: No.280 歯車の問題(1)
// 2019.5.4 bal4u

#include <stdio.h>

#if 1
#define gc() getchar_unlocked()
#else
#define gc() getchar()
#endif
long long in()    // 非負整数の入力
{
	long long n = 0;
	int c = gc();
	do n = 10 * n + (c & 0xf), c = gc(); while (c >= '0');
	return n;
}

long long gcd(long long a, long long b)
{
	long long r;
	while (b != 0) r = a % b, a = b, b = r;
	return a;
}

void norm(long long *a, long long *b)
{
	long long g = gcd(*a, *b);
	if (g > 1) *a /= g, *b /= g;
}

int main()
{
	int N;
	long long p, a, b, aa, bb;
	
	N = (int)in()-2;
	a = in(), b = p = in(), norm(&a, &b);
	while (N--) {
		aa = p, bb = p = in(), norm(&aa, &bb);
		a *= aa, b *= bb, norm(&a, &b);
	}
	printf("%lld/%lld\n", b, a);
	return 0;
}