// URL: https://yukicoder.me/problems/no/797 import std.algorithm, std.container, std.math, std.range, std.typecons, std.string; const mod = 10^^9+7; alias mint = ModInt!mod; version(unittest) {} else void main() { int n; io.getV(n); int[] a; io.getA(n, a); auto fact = Fact!mint(n), r = mint(0); foreach (i, ai; a) r += fact.combi(n-1, i) * ai; io.put(r); } struct Fact(T, bool noInv = false) { size_t n; T[] table, invTable; this(size_t n) { this.n = n; table = new T[](n+1); table[0] = 1; foreach (i; 1..cast(int)n+1) table[i] = table[i-1]*i; static if (!noInv) { invTable = new T[](n+1); invTable[n] = T(1)/table[n]; foreach_reverse (i; 1..cast(int)n+1) invTable[i-1] = invTable[i]*i; } } auto perm(size_t a, size_t b) in { assert(!noInv && n >= a && a >= b); } body { return table[a]*invTable[a-b]; } auto combi(size_t a, size_t b) in { assert(!noInv && n >= a && a >= b); } body { return table[a]*invTable[b]*invTable[a-b]; } auto homo(size_t a, size_t b) in { assert(!noInv && n >= a+b-1); } body { return combi(a+b-1, b); } } struct ModInt(int m, bool pos = false) { version(BigEndian) union { long l; struct { int i2; int i; } } else union { long l; int i; } alias M = ModInt!(m, pos); @property static init() { return M(0); } @property int value() { return i; } @property void value(int v) { i = mod(v); } alias value this; this(int v) { i = v; } this(int v, bool runMod) { i = runMod ? mod(v) : v; } this(long v) { i = mod(v); } ref auto opAssign(int v) { i = v; return this; } pure auto mod(int v) const { static if (pos) return v%m; else return (v%m+m)%m; } pure auto mod(long v) const { static if (pos) return cast(int)(v%m); else return cast(int)((v%m+m)%m); } static if (!pos) pure auto opUnary(string op: "-")() { return M(mod(-i)); } static if (m < int.max / 2) { pure auto opBinary(string op)(int r) if (op == "+" || op == "-") { return M(mod(mixin("i"~op~"r"))); } ref auto opOpAssign(string op)(int r) if (op == "+" || op == "-") { i = mod(mixin("i"~op~"r")); return this; } } else { pure auto opBinary(string op)(int r) if (op == "+" || op == "-") { return M(mod(mixin("l"~op~"r"))); } ref auto opOpAssign(string op)(int r) if (op == "+" || op == "-") { i = mod(mixin("l"~op~"r")); return this; } } pure auto opBinary(string op: "*")(int r) { return M(mod(l*r)); } ref auto opOpAssign(string op: "*")(int r) { i = mod(l*r); return this; } pure auto opBinary(string op)(M r) if (op == "+" || op == "-" || op == "*") { return opBinary!op(r.i); } ref auto opOpAssign(string op)(M r) if (op == "+" || op == "-" || op == "*") { return opOpAssign!op(r.i); } pure auto opBinary(string op: "/")(M r) { return M(mod(l*r.inv.i)); } ref auto opOpAssign(string op: "/")(M r) { i = mod(l*r.inv.i); return this; } pure auto opBinary(string op: "/")(int r) { return opBinary!op(M(r)); } ref auto opOpAssign(string op: "/")(int r) { return opOpAssign!op(M(r)); } pure auto opBinary(string op: "^^", U)(U n) { auto x = M(1); if (n == 0) return x; auto b = M(i); for (; n > 0; n >>= 1) { if (n&1) x *= b; b *= b; } return x; } pure auto inv() { int x = i, a, b; exEuclid(x, m, a, b); return M(mod(a)); } pure int exEuclid(int a, int b, ref int x, ref int y) { auto g = a; x = 1; y = 0; if (b) { g = exEuclid(b, a%b, y, x); y -= a/b*x; } return g; } } auto io = IO(); struct IO { import std.algorithm, std.conv, std.format, std.meta, std.range, std.stdio, std.traits; dchar[] buf; auto sp = (new dchar[](0)).splitter; int precision = 10; string delimiter = " "; void nextLine() { stdin.readln(buf); sp = buf.splitter; } auto get(T)(ref T v) { if (sp.empty) nextLine(); v = sp.front.to!T; sp.popFront(); } auto getV(T...)(ref T v) { foreach (ref w; v) get(w); } auto getA(T)(size_t n, ref T v) if (hasAssignableElements!T) { v = new T(n); foreach (ref w; v) get(w); } auto getC(T...)(size_t n, ref T v) if (allSatisfy!(hasAssignableElements, T)) { foreach (ref w; v) w = new typeof(w)(n); foreach (i; 0..n) foreach (ref w; v) get(w[i]); } auto getM(T)(size_t r, size_t c, ref T v) if (hasAssignableElements!T && hasAssignableElements!(ElementType!T)) { v = new T(r); foreach (ref w; v) getA(c, w); } auto rangePop(R)(ref R r) { r.popFront(); if (!r.empty) write(delimiter); } auto putA(T)(T v) { static if (isInputRange!T && !isSomeString!T) for (auto w = v; !w.empty; rangePop(w)) putA(w.front); else if (isFloatingPoint!T) writef(format("%%.%df", precision), v); else write(v); } auto put(T...)(T v) { foreach (i, w; v) { putA(w); if (i < v.length-1) write(delimiter); } writeln; } auto putB(S, T)(bool c, S t, T f) { if (c) put(t); else put(f); } auto dbg(T...)(T v) { stderr.writeln(v); } }