#include "bits/stdc++.h"
using namespace std;
#define int long long
const int MAXN = 3e5 + 10;
const int MOD = 1e9 + 7;
#define ll __int128
mt19937_64 rng((int)std::chrono::steady_clock::now().time_since_epoch().count());
int rnd(int x, int y) {
int u = uniform_int_distribution<int>(x, y)(rng); return u;
}
ll read() { int x; cin >> x; return (ll)x; }
long long bm(long long b, long long p) {
if(p==0) return 1 % MOD;
long long r = bm(b, p >> 1);
if(p&1) return (((r*r) % MOD) * b) % MOD;
return (r*r) % MOD;
}
long long inv(long long b) {
return bm(b, MOD-2);
}
long long f[MAXN];
long long nCr(int n, int r) {
long long ans = f[n]; ans *= inv(f[r]); ans %= MOD;
ans *= inv(f[n-r]); ans %= MOD; return ans;
}
long long fib[MAXN], lucas[MAXN];
void precomp() {
for(int i=0; i<MAXN; i++) f[i] = (i == 0 ? 1 % MOD : (f[i-1] * i) % MOD);
lucas[0] = 2;
lucas[1] = 1;
for(int i=2; i<MAXN; i++) lucas[i] = (lucas[i-2] + lucas[i-1]) % MOD;
fib[0] = 0;
fib[1] = 1;
for(int i=2; i<MAXN; i++) fib[i] = (fib[i-2] + fib[i-1]) % MOD;
}
int fastlog(int x) {
return (x == 0 ? -1 : 64 - __builtin_clzll(x) - 1);
}
void gay(int i) { cout << "Case #" << i << ": "; }
int csb(int l, int r, int k) { // count number of [l, r] such that i & 2^k > 0
if(l > r) return 0;
if(l == 0) {
int s = r / (1ll << (k+1)); // number of complete cycles
int t = r % (1ll << (k+1));
int ans = s * (1ll << k);
ans += (t >= (1ll << k) ? t - (1ll << k) + 1 : 0);
return ans;
}
else return csb(0, r, k) - csb(0, l - 1, k);
}
int lis(vector<int> a) {
int n = a.size();
int bucket[n+1];
for(int i=1; i<=n; i++) bucket[i] = 1e18;
int ans = 1;
for(int x: a) {
auto it = lower_bound(bucket + 1, bucket +n +1, x);
int d = distance(bucket, it);
ans = max(ans, d);
bucket[d] = min(bucket[d], x);
}
return ans;
}
bool cmp(pair<int, char> a, pair<int, char> b) {
if(a.first != b.first) return a.first < b.first;
return a.second > b.second;
}
void solve(int tc) {
int N;
cin >> N;
ll A, B;
A =read();
B =read();
ll g = gcd((int) A, (int) B + 1);
ll len = A / g;
vector<pair<ll, char> > segments;
for(int i=0; i<N; i++) {
ll L, R;
L = read();
R = read();
if(R - L + 1 > B * len) {
cout << (int) (B * len) << "\n";
return;
}
else if(L % (B * len) > R % (B * len)) {
segments.emplace_back(L % (B * len), 'S');
segments.emplace_back(B * len - 1, 'E');
segments.emplace_back(0, 'S');
segments.emplace_back(R % (B * len), 'E');
}
else {
segments.emplace_back(L % (B * len), 'S');
segments.emplace_back(R % (B * len), 'E');
}
}
sort(segments.begin(), segments.end(), cmp);
int ans = 0;
int str = -1;
int bal = 0;
for(pair<ll, char> x: segments) {
if(x.second == 'S') {
bal++;
if(bal == 1) str = x.first;
}
else {
bal--;
if(bal == 0) ans += x.first - str + 1;
}
}
cout << ans << "\n";
}
int32_t main() {
precomp();
ios::sync_with_stdio(0); cin.tie(0);
int t = 1; //cin >> t;
for(int i=1; i<=t; i++) solve(i);
}
// I don't know geometry.
// Teaming is unfair.
Compilation message
strange_device.cpp: In function 'void solve(long long int)':
strange_device.cpp:74:10: error: 'gcd' was not declared in this scope
74 | ll g = gcd((int) A, (int) B + 1);
| ^~~
