// code of JUYU ^ ^ never doubt youself !
#include <bits/stdc++.h>
typedef long long ll;
#define int ll
#define For(i,a,b) for (int i = a; i <= b; i ++)
#define Dow(i,a,b) for (int i = b; i >= a; -- i)
#define ms(a,b) memset(a, b, sizeof (a))
#define fir first
#define sec second
#define mk make_pair
#define pb push_back
#define eb emplace_back
using namespace std;
typedef pair<int,int> PII;
const int mod = 998244353;
const int MOD = 1000000007;
const int maxn = 2e5 + 5;
const double inf = 1e18;
inline ll read()
{
ll t = 0, dp = 1; char c = getchar();
while(!isdigit(c)) {if (c == '-') dp = -1; c = getchar();}
while(isdigit(c)) t = t * 10 + c - 48, c = getchar();
return t * dp;
}
inline void write(ll x){if (x < 0){putchar('-'); x = -x;} if(x >= 10) write(x / 10); putchar(x % 10 + 48);}
inline void writeln(ll x){write(x); puts("");}
inline void write_p(ll x){write(x); putchar(' ');}
inline void write_b(ll x){putchar(' '); write(x);}
inline int qpow(int x, int y, int z){int ret = 1; for (; y; y /= 2, x = x * x % z) if (y & 1) ret = ret * x % z; return ret;}
inline int PrimeInv(int x, int y, int z){return qpow(x, y - 2, z);}
signed main()
{
int N = read(), S = read(), T = read(), A = read(), B = read();
double low = B, up = inf;
For(cnt,0,99)
{
double mid = (low + up) / 2;
int num = min(T, (int)mid / A + 1);
double avg = (double)A * (num * (num - 1)) / (2 * N) + mid * (1 - ((double)num / N));
if (avg + B > mid) low = mid;
else up = mid;
}
double ans = low;
if (S <= T) ans = min(ans, (double)A * (T - S));
printf("%.16lf\n", ans);
return 0;
}
/* stuff you should look for
* int overflow, array bounds
* special cases (n=1?)
* do smth instead of nothing and stay organized
* WRITE STUFF DOWN
* DON'T GET STUCK ON ONE APPROACH
-- Benq
*/