CSES – Tasks and Deadlines

#include<bits/stdc++.h>
#define int long long
#define double long double
#define f first
#define s second
#define fastio ios_base::sync_with_stdio(false);cin.tie(0)
using namespace std;
//declare

//
signed main(){
    fastio;
    int n; cin>>n;
    vector<pair<int,int>>v(n);
    for(int i=0;i<n;i++){
        cin>>v[i].f>>v[i].s;
    }
    sort(v.begin(),v.end());
    int now=0, ans=0;
    for(int i=0;i<n;i++){
        now += v[i].f;
        ans += v[i].s - now;
    }
    cout<<ans<<"\n";
    return 0;
}