// Example program
#include <iostream>
#include <string>

using namespace std;

/*long long gcd(long long a, long long b){
    long long r = 0;
    while (b != 0)
    {
        r = a % b;
        a = b;
        b = r;
    }
    return a;
}
**/
int main()
{
long long n, a, b, count = 0;
cin >> n >> a >> b;
long long  n2 = 0, n3 = 0;

if (n % 2 == 0) n2 = n/2;
else {
    n3 = 1;
    n -= 3;
    n2 = n/2;
}


//n2 - step 3;  n3 + step 2
while (n3 * n2 >= 0){
    if (n2 <= a && n3 <= b) count++;
    n2 -= 3;
    n3 += 2;
}


if (count == (a + 1) * (b + 1)) cout << 1;
else if(count == 0) cout << 0;
else {
    long long g = 1;//gcd(count, (a+1)*(b+1));
    cout << count / g  << '/' << (a + 1) * (b + 1) / g;
}
}