import std.algorithm, std.container, std.conv, std.math, std.range, std.typecons, std.stdio, std.string; auto rdsp(){return readln.splitter;} void pick(R,T)(ref R r,ref T t){t=r.front.to!T;r.popFront;} void readV(T...)(ref T t){auto r=rdsp;foreach(ref v;t)pick(r,v);} void readA(T)(size_t n,ref T[]t){t=new T[](n);auto r=rdsp;foreach(ref v;t)pick(r,v);} void main() { int n, l; readV(n, l); string[] st; readA(n, st); l *= 60; auto s = st.map!(sti => sti[0..2].to!int*60+sti[3..5].to!int).array; if (s.sum < l) { writeln(n); return; } auto dp1 = new long[][][](n+1, n+1, l); dp1[0][0][0] = 1; foreach (i; 0..n) foreach (j; 0..n+1) foreach (k; 0..l) { dp1[i+1][j][k] = dp1[i][j][k]; if (j >= 1 && k >= s[i]) dp1[i+1][j][k] += dp1[i][j-1][k-s[i]]; } auto fact = new real[](n+1); fact[0] = 1; foreach (i; 1..n+1) fact[i] = fact[i-1]*i; auto r = 0.0L, dp2 = new long[][](n+1, l); foreach (i; 0..n) { foreach (j; 0..n+1) foreach (k; 0..l) { dp2[j][k] = dp1[n][j][k]; if (j >= 1 && k >= s[i]) dp2[j][k] -= dp2[j-1][k-s[i]]; } foreach (j; 0..n) foreach (k; l-s[i]..l) r += dp2[j][k]*fact[j+1]*fact[n-1-j]; } writefln("%.10f", r/fact[n]); }