#include<iostream> using namespace std; int main(){ int n; cin>>n; for(int i=1;i<=n;i++){ cin>>m[i][1]>>m[i][2]; } int sum=0,minn=99999; for(int i=1;i<=n;i++) { if(m[i][1]<minn) minn=m[i][1]; sum+=minn; minn=m[i][2]; } cout<<sum; return 0; }