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