#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,s=0,min=10000; cin>>n; for(int i=1;i<=n;i++){ int a,b; cin>>a>>b; if(b<=min){ min=b; } s+=min*a; } cout<<s; return 0; }