157 lines
2.9 KiB
C++

/* Problem URL: https://codeforces.com/contest/450/problem/B */
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
template <class T, class comp = less<>>
using ordered_set = tree<T, null_type , comp , rb_tree_tag , tree_order_statistics_node_update>;
#define V vector
#define rmin(a, b) a = min(a, b)
#define rmax(a, b) a = max(a, b)
#define rep(i, lim) for (int i = 0; i < (lim); i++)
#define nrep(i, s, lim) for (int i = s; i < (lim); i++)
#define repv(i, v) for (auto &i : (v))
#define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; }
#define sortv(v) sort(v.begin(), v.end())
#define all(v) (v).begin(), (v).end()
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vvvvi = vector<vvvi>;
using ll = long long;
using vl = vector<ll>;
using vvl = vector<vl>;
using vvvl = vector<vvl>;
using vvvvl = vector<vvvl>;
template<class v>
auto operator<<(ostream &os, const vector<v> &vec)->ostream& {
os << vec[0];
for (size_t i = 1; i < vec.size(); i++) {
os << ' ' << vec[i];
}
os << '\n';
return os;
}
template<class v>
auto operator>>(istream &is, vector<v> &vec)->istream& {
for (auto &i : vec) {
is >> i;
}
return is;
}
template<class v>
auto operator<<(ostream &os, const vector<vector<v>> &vec)->ostream& {
for (auto &i : vec) {
os << i[0];
for (size_t j = 1; j < i.size(); j++) {
os << ' ' << i[j];
}
os << '\n';
}
return os;
}
template<class v>
auto operator>>(istream &is, vector<vector<v>> &vec)->istream& {
for (auto &i : vec) {
for (auto &j : i) {
is >> j;
}
}
return is;
}
const int oo = INT32_MAX >> 1;
const ll OO = INT64_MAX >> 1;
void pre()
{
}
#define TEST 0
void solve()
{
ll x, y, n;
cin >> x >> y >> n;
const ll mod = 1e9 + 7;
if (n == 1) {
cout << x + mod * (x < 0) << '\n';
return;
}
if (n == 2) {
cout << y + mod * (y < 0) << '\n';
return;
}
n -= 2;
auto mul = [&](vvl &a, vvl &b) {
vvl c(a.size(), vl(b[0].size()));
rep(i, c.size()) {
rep(j, c[0].size()) {
rep(k, b.size()) {
c[i][j] = ((c[i][j] + a[i][k] * b[k][j] % mod) % mod + mod) % mod;
}
}
}
return c;
};
auto fpow = [&]() {
vvl ans = {{x}, {y}};
vvl mu(2, vl(2));
mu[0][1] = 1;
mu[1][0] = mod - 1;
mu[1][1] = 1;
rep(i, 31) {
if ((n >> i) & 1) {
ans = mul(mu, ans);
}
mu = mul(mu, mu);
}
return ans;
};
auto ans = fpow();
cout << ans[1][0] << '\n';
}
int main()
{
ios::sync_with_stdio(false);
cin.tie(nullptr);
pre();
int t;
(TEST && cin >> t) || (t = 1);
while (t--) {
solve();
}
}