#include<bits/stdc++.h>
using namespace std;
#pragma GCC optimize("O3")
#define tof_io ios_base::sync_with_stdio(false);cin.tie(0) , cout.tie(0);
#define double long double
#define int long long
#define pb push_back
#define all(x) x.begin(),x.end()
#define endl '\n'
#define sz(x) x.size()
//const int mod = 998244353; //998244353 1e9+7 1e9+9
const int N = 1e7 + 23;
const int lg = 23;
const int inf = 2e18;
int fac[N];
int inv[N];
int a[N];
int ans = 0;
//int dnt_pow (int a, int b, int md = mod){int ans = 1; while(b){if(b&1){ans = (a*ans)%md;}a = (a*a)%md;b >>= 1;}return ans ;}
//void dnt_bld (){fac[0] = 1; inv[0] = dnt_pow(fac[0],mod-2) ;for(int i = 1 ; i < N ; i++) {fac[i] = (fac[i-1] * i) % mod;inv[i] = dnt_pow( fac[i] , mod-2);}}
//int dnt_ncr (int r,int n){if(r>n) return 0; return fac[n] * inv[r] % mod * inv[n-r] % mod;}
int32_t main()
{
int n;
cin >> n;
for(int i = 0; i < n; i++)
{
int x,y;
cin >> x >> y;
a[x] = max(a[x], y);
}
int mx = 0;
for(int i = 1e7; i >= 1; i--)
{
mx = max(mx, a[i]);
ans = ans + mx;
}
cout << ans;
}
