#include<stdio.h>
int main()
{
int n;
int t=0;
int a[n]={0},b[n]={0},c[n]={0},d[n]={0};
scanf("%d\n",&n);
for(int i=0;i<n;i++){
scanf("%d %d",&a[i],&b[i]);
c[i]=a[i]+b[i]-8;
}
d[0]=c[0];
for(int x=1;x<n;x++){
d[x]=d[x-1]+c[x];
t+=d[x];
}
t+=d[0];
printf("%d",t);
}