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OI-codes/S2OJ/1665/1665.cpp

49 lines
840 B
C++

#include <iostream>
using std::cin;
using std::cout;
const char endl = '\n';
const int N = 1e6 + 5;
const int mod = 1e9 + 7;
int n;
long long f[N], ans;
int main() {
std::ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n;
if (n == 1) {
cout << 1 << endl;
exit(0);
}
f[1] = 1;
for (int j = 1; j < n; j++) {
if (j <= 3) {
for (int i = j + 1; i < n; i++) {
f[i] = (f[i] + f[j]) % mod;
}
} else {
for (int k = -1; k <= 1; k++) {
for (int i = j + k; i < n; i += j) {
if (j < i) f[i] = (f[i] + f[j]) % mod;
}
}
}
}
for (int i = 1; i < n; i++) {
ans = (ans + f[i]) % mod;
}
cout << ans * n % mod << endl;
return 0;
}