#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,b,num=0,min=101; cin>>n; for(int i=1;i<=n;i++){ cin>>a>>b; if(min>b) min=b; num+=a*min; } cout<<num<<endl; return 0; }