Problem Link : http://www.lightoj.com/volume_showproblem.php?problem=1221

/*
         +-+ +-+ +-+
         |R| |.| |S|
         +-+ +-+ +-+
 */

#include <bits/stdc++.h>

#define pii             pair <int,int>
#define sc              scanf
#define pf              printf
#define Pi              2*acos(0.0)
#define ms(a,b)         memset(a, b, sizeof(a))
#define pb(a)           push_back(a)
#define MP              make_pair
#define db              double
#define ll              long long
#define EPS             10E-10
#define ff              first
#define ss              second
#define sqr(x)          (x)*(x)
#define D(x)            cout<<#x " = "<<(x)<<endl
#define VI              vector <int>
#define DBG             pf("Hi\n")
#define MOD             100007
#define MAX             105
#define CIN             ios_base::sync_with_stdio(0)
#define SZ(a)           (int)a.size()
#define sf(a)           scanf("%d",&a)
#define sff(a,b)        scanf("%d%d",&a,&b)
#define sfff(a,b,c)     scanf("%d%d%d",&a,&b,&c)
#define loop(i,n)       for(int i=0;i<n;i++)
#define REP(i,a,b)      for(int i=a;i<b;i++)
#define TEST_CASE(t)    for(int z=1;z<=t;z++)
#define PRINT_CASE      printf("Case %d: ",z)
#define all(a)          a.begin(),a.end()
#define intlim          2147483648
#define inf             1000000
#define ull             unsigned long long

using namespace std;

vector<int>from,to,cost;
int d[MAX];

int main()
{
    ///freopen("in.txt","r",stdin);
    ///freopen("out.txt","w",stdout);
    int t;
    sf(t);
    TEST_CASE(t)
    {
        int n,r,p;
        sfff(n,r,p);
        int a,b,income,expence;
        loop(i,r)
        {
            sc("%d %d %d %d",&a,&b,&income,&expence);
            from.pb(a);
            to.pb(b);
            cost.pb(p*expence-income);
        }

        bool test=0;
        for(int j=1;j<=n;j++)
        {
            for(int i=0;i<r;i++)
            {
                int temp=d[from[i]]+cost[i];
                if(temp<d[to[i]])
                {
                    if(j==n) test=1;
                    d[to[i]]=temp;
                }
            }
        }

        PRINT_CASE;
        if(test)
            pf("YES\n");
        else
            pf("NO\n");

        ms(d,0);
        from.clear();
        to.clear();
        cost.clear();
    }
    return 0;
}

This problem can be solved using Floyed Warshal algorithm. Another solution is Here Light OJ 1221 – Travel Company (Floyed Warshal)