#include<iostream> #include<cstdio> //scanf()\printf() #include<cstring> #include<cmath> //sqrt()\pow()\abs()\ceil()\floor()\max()\min() using namespace std; int main(){ int n=1001,a[n],b[n],s=0; cin>>n; for(int i=1;i<=n;i++){ cin>>a[i]; cin>>b[i]; s+=a[i]*b[i]; } cout<<s; return 0; }