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OI-codes/Luogu/P4777/P4777.cpp

60 lines
1.0 KiB
C++

#include <iostream>
#include <algorithm>
using std::cin;
using std::cout;
const char endl = '\n';
int n;
long long a1, b1, a2, b2;
long long exgcd(long long a, long long b, long long &x, long long &y) {
if (!b) {
x = 1, y = 0;
return a;
}
long long g = exgcd(b, a % b, y, x);
y -= a / b * x;
return g;
}
int main() {
std::ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n;
for (int i = 1; i <= n; i++) {
cin >> b2 >> a2;
if (i == 1) {
b1 = b2;
a1 = a2;
} else {
long long x, y,
g = exgcd(b1, b2, x, y),
c = a2 - a1,
m1 = b2 / g,
m2 = b1 / g * b2;
if (c % g) {
cout << -1 << endl;
exit(0);
}
x = static_cast<__int128>(x) * c / g % m1;
a1 = ((a1 + b1 * x) % m2 + m2) % m2;
b1 = m2;
}
}
cout << a1 % b1 << endl;
return 0;
}