#include<stdio.h>
int main()
        {
        long long unsigned i,n,t,s=0,x,y;
        FILE*f=fopen("branza.in","r");
        FILE*g=fopen("branza.out","w");
        fscanf(f,"%llu %llu %llu",&n,&t,&s);
        s=0;
        for(i=1;i<=n;++i)
                {
                fscanf(f,"%llu %llu",&x,&y);
                s+=x*y;
                }
         fprintf(g,"%llu",s);
         return 0;
         }