strange_device.cpp:9:1: error: expected initializer before 'stack'
stack <pair <ll, ll> > s;
^~~~~
strange_device.cpp: In function 'bool inter(long long int, long long int)':
strange_device.cpp:13:10: error: 's' was not declared in this scope
ll x = s.top().first;
^
strange_device.cpp: In function 'int main()':
strange_device.cpp:19:35: error: 'b' was not declared in this scope
scanf ("%d %lld %lld", &n, &a, &b);
^
strange_device.cpp:25:9: error: 's' was not declared in this scope
if (s.empty() || !inter(t[i].first, t[i].second)) {
^
strange_device.cpp:36:10: error: 's' was not declared in this scope
while (s.size()) {
^
strange_device.cpp:21:11: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf ("%lld %lld", &t[i].first, &t[i].second);
~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~