#include<bits/stdc++.h> using namespace std; int m[100]; int n1[100]; int main(){ int n; cin>>n; for(int i=1;i<=n;i++){ cin>>m[i]>>n1[i]; } int minn=999999; int sum=0; for(int i=1;i<=n;i++){ if(m[i]<minn){ minn=m[i]; } sum+=minn; minn+=n1[i]; } cout<<sum; return 0; }