Russian Code Cup 2013 Qualification 2, problem C

gistfile1.cpp

#include <cstdio> 

#define FOR(i,f,n) for(int i=f; i<n; ++i) 

int N, M, K, L, S, V;

int main()
{
    //freopen("in.txt", "r", stdin);
    //freopen("out.txt", "w", stdout);

  while (true)
	{
		scanf("%d%d%d%d", &N, &L, &S, &V);
		if (N == 0)
			break;
		double res = S / (0.0 + V);
		int len = 0;
		FOR(i,0,N)
		{
			int x, l, v;
			scanf("%d%d%d", &x, &l, &v);

			len += L + l;

			double r = (S + len - x) / (v + 0.0);
			res = max(res, r);
		}
		printf("%.9lf\n", res);
	}

    return 0;
}