#include<iostream> // cin\cout\endl #include<cstdio> //scanf()\printf() #include<cstring> // strcpy()\strcat()\strcmp()\strlen()\memset() #include<cmath> //sqrt()\pow()\abs()\ceil()\floor()\max()\min() using namespace std; int main(){ int n,a=0,b=0,c=0,f=1000000000; cin>>n; for(int i=1;i<=n;i++){ cin>>a>>b; c+=a*b; } cout<<c; return 0; }