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- #include <iostream>
- using namespace std;
- int gcd(int a, int b, int &x, int &y) {
- if (a == 0) {
- x = 0; y = 1;
- return b;
- }
- int x1, y1;
- int d = gcd (b%a, a, x1, y1);
- x = y1 - (b / a) * x1;
- y = x1;
- return d;
- }
- int main(){
- int n, p;
- cin >> n >> p;
- int r = 0;
- for(int i = 1; i <= n; ++i){
- int x, y;
- gcd(i, p, x, y);
- if(x < 0){
- x = (-x)*(p-1)%p;
- }
- r += x;
- }
- cout << r;
- return 0;
- }
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