#include<iostream> using namespace std; int main() { int n,i,min = 10001,sum = 0; int a[101]={0,},b[101] = {0,}; cin >> n; for(i = 0 ; i < n;i++) cin >> a[i] >> b[i]; for(i = 0 ; i < n;i++) { if(min > a[i]) min = a[i]; sum += min; min += b[i]; } cout << sum << endl; return 0; }