Task

#include <stdio.h>
#include <iostream>
#include <memory.h>
#include <string.h>
#include <math.h>
#include <algorithm>
#include <set>
#include <map>
#include <string>
#include <vector>


#define INPUT_FILE "input.txt"
#define OUTPUT_FILE "output.txt"
#define clear(x) memset(x,0,sizeof(x))
#define fill(a,b) memset(a,b,sizeof(a))
#define Forn(i,y) for (int i=0; i<(y); i++)
#define Fornr(i,y) for (int i=(y)-1; i>=0; i--)
#define Forp(i,x,y) for (int i=(x); i<=(y); i++)
#define Forpr(i,x,y) for (int i=(x); i>=(y);i--)
#define pb push_back

typedef long long ll;
typedef std::pair< int, int> pii;
const int INF = 2147483647;
const int MaxC = 200010;

using namespace std;

int phi(int x)
{
    if (x==1) return 2;
    int result=x;
    for (int i=2; i*i<=x; i++)
        if (x%i==0)
        {
            while (x%i==0) x/=i;
            result-=result/i;
        }
    if (x>1) result-=result/x;
    return result;
}

int gcd(int a, int b)
{
    while (b)
    {
        a%=b;
        swap(a,b);
    }
    return a;
}

int main()
{
    #ifndef ONLINE_JUDGE
    freopen(INPUT_FILE,"r",stdin);
    freopen(OUTPUT_FILE,"w",stdout);
    #endif

    ll n;
    scanf("%I64d",&n);
    while (n!=0)
    {
        ll ans=0,pre;
        int m=0;
        for (int i=1; i<=MaxC; i++)
        {
            pre=(ll)phi(i);
            if (n<=ans+pre)
            {
                m=i;
                break;
            }
            else
                ans+=pre;
        }
        ll q=0;
        for (int i=0; i<=m; i++)
        {
            q+=(gcd(i,m)==1);
            if (ans+q==n)
            {
                printf("%d/%d\n",i,m);
                break;
            }
        }
        scanf("%I64d",&n);
    }

    #ifdef ONLINE_JUDGE
    fclose(stdin); fclose(stdout);
    #endif