#include<iostream> using namespace std; int n,sum; int main(){ cin>>n; int f[105],y[105]; int min=100000000; for(int i=0;i<n;i++){ cin>>f[i]>>y[i]; } for(int i=0;i<n;i++){ if(f[i]<min){ min=f[i]; } sum+=min; min+=y[i]; } cout<<sum; return 0; }