/*
int       %d
longlong  %lld
float     %f
double    %lf
char      %c
char[]    %s
'a'=97
'z'=122
'A'=65
'Z'=90
'0'=48
'9'=57
*/
#include <iostream>
#include <iomanip>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int N=1e5+10;
const int INF=0x3f3f3f3f;
int n,x,y,a[N],b[N],c[N];
int len;
int main(){
	scanf("%d",&n);
	for(int i=1;i<=n;i++){
		scanf("%d%d",&x,&y);
		a[n-i]=x;
		b[n-i]=y;
	}
	x=0;
	for(int i=0;i<n;i++){
		c[i]=a[i]+b[i]+x;
		x=c[i]/10;
		c[i]%=10;
	}
	len=n-1;
	if(x){
		c[++len]=x;
	}
	for(int i=len;i>=0;i--){
		printf("%d",c[i]);
	}
return 0;
}