#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<cmath>
#define ll long long
using namespace std;
const int MN=2e6+5;
ll n,t[MN],x[MN],maxn;
void write(ll n){if(n<0){putchar('-');write(-n);return;}if(n>9)write(n/10);putchar(n%10+'0');}
ll read(){ll x=0,f=1;char ch=getchar();while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}while(ch>='0'&&ch<='9'){x=(x<<1)+(x<<3)+(ch^48);ch=getchar();}return x*f;}
int main(){
    n=read();
    for(int i=1; i<=n; i++){
        t[i]=read();x[i]=read();
        maxn=max(maxn,x[i]);
    }
    write(t[n]+maxn*2);putchar('\n');
    return 0;
}