#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,i,j,min=1001,s=0,sum=0; cin>>n; int a[n],b[n]; for(i=1;i<=n;i++){ cin>>a[i]>>b[i]; s+=a[i]; if(b[i]<min){ min=b[i]; } sum+=s*min; s=0; } cout<<sum; return 0; }