// yuki 904 サメトロ
// 2019.10.11 bal4u

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

#define gc() getchar()
#define pc(c) putchar(c)

int in() {  // 整数の入力
	int n = 0, c = gc();
	while (isspace(c)) c = gc();
	if (c == '-') {	c = gc();
		do n = 10*n + (c & 0xf), c = gc(); while (c >= '0');
		return -n;
	}
	do n = 10*n + (c & 0xf), c = gc(); while (c >= '0');
	return n;
}

int SA, SB;

int main()
{
	int i, A, B, N, f, ma;
	
	N = in();
	f = 1, ma = 0;
	SA = SB = 0; for (i = 2; i <= N; i++) {
		A = in(), B = in();
		if (A > ma) ma = A;
		SA += A, SB += B;
		if (A != B) f = 0;
	}
	if (f) {
		if (SA - ma < ma) SA -= SA-ma;
	} else if (SA > SB) SA = SB;
	printf("%d\n", SA+1);
	return 0;
}