#include

#include

#include

using namespace std;

int main() {

int n;

cin >> n;




vector<vector<int>> v;


for(int i=0; i<n; i++){

    int a, b;
    
    cin >> a >> b;
    
    v.push_back({a, b});
    
}

sort(v.begin(), v.end());
vector<vector<int>> ans;
int start = v[0][0], end = v[0][1];


for(int i=1; i<n; i++){
    if(v[i][0] <= end){ 
        if(v[i][1] > end) end = v[i][1];
    } else {  
        ans.push_back({start, end});  
        start = v[i][0];
        end = v[i][1];
    }
}
ans.push_back({start, end});  
cout << ans.size() << endl;
for(auto x: ans){
    cout << x[0] << " " << x[1] << endl;
}

return 0;

}