#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <algorithm>
typedef long long ll ;
#define rep(i, a, b) for (int i = a; i <= b; ++ i) 
const int N = 2e5 + 5, inf = 1e9 + 7 ;
using namespace std ;

int na, mo, n = 0, d[N], tr[N << 2] ;
ll fl[N], fr[N] ;
struct poi {
	int l, r ; 
} a[N] ;

int find(int x) {
	int l = 1, r = d[0] ;
	for ( ; l <= r ; ) {
		int mid = (l + r) / 2 ;
		if (d[mid] == x) return mid ;
		if (x < d[mid]) r = mid - 1 ; else l = mid + 1 ;
	}
	return 0 ;
}

void pre() {
	d[0] = 0 ;
	rep(i, 0, n - 1) d[++ d[0]] = a[i].l, d[++ d[0]] = a[i].r ;
	sort(d + 1, d + d[0] + 1) ;
	d[0] = unique(d + 1, d + d[0] + 1) - (d + 1) ;
	rep(i, 0, n - 1) a[i].l = find(a[i].l), a[i].r = find(a[i].r) ;
}

void build(int p, int l, int r) {
	tr[p] = inf ;
	if (l == r) return ;
	int mid = (l + r) / 2 ;
	build(p << 1, l, mid), build(p << 1 | 1, mid + 1, r) ;
}

void modify(int p, int l, int r, int lx, int rx, int ave) {
	if (l == lx && r == rx) {
		tr[p] = min(tr[p], ave) ;
		return ;
	}
	int mid = (l + r) / 2 ;
	if (rx <= mid) modify(p << 1, l, mid, lx, rx, ave) ; else
	if (lx > mid) modify(p << 1 | 1, mid + 1, r, lx, rx, ave) ; else
		modify(p << 1, l, mid, lx, mid, ave), modify(p << 1 | 1, mid + 1, r, mid + 1, rx, ave) ;
}

int query(int p, int l, int r, int pos) {
	int ret = tr[p] ;
	if (l == r) return ret ;
	int mid = (l + r) / 2 ;
	if (pos <= mid) ret = min(ret, query(p << 1, l, mid, pos)) ; 
		else ret = min(ret, query(p << 1 | 1, mid + 1, r, pos)) ;
	return ret ;
}

int main() {
	scanf("%d%d", &na, &mo) ;
	int x, y, las = 0 ; ll sum = 0 ;
	rep(i, 1, na) {
		scanf("%d%d", &x, &y) ;
		las = (las + x) % mo, sum += x ;
		if (x * 2 > mo && (y & 1)) { puts("-1") ; return 0 ; }
		if (y & 1) a[n].l = (- 2 * (las - x) % mo + mo) % mo, a[n].r = (- 2 * las % mo + mo) % mo, ++ n ; else
			a[n].l = 0, a[n].r = mo - 1, ++ n ;
	}
	pre() ;
	build(1, 1, d[0]) ;
	for (int i = n - 1 ; i >= 0; -- i) {
		int u = query(1, 1, d[0], a[i].l) ;
		if (u == inf) fl[i] = 0 ; else fl[i] = fl[u] + (d[a[u].l] - d[a[i].l] + mo) % mo ;
		u = query(1, 1, d[0], a[i].r) ;
		if (u == inf) fr[i] = 0 ; else fr[i] = fl[u] + (d[a[u].l] - d[a[i].r] + mo) % mo ;
		fl[i] = min(fl[i], fr[i] + (d[a[i].r] - d[a[i].l] + mo) % mo) ;
		fr[i] = min(fr[i], fl[i] + (d[a[i].l] - d[a[i].r] + mo) % mo) ;
		if (a[i].l <= a[i].r) {
			if (a[i].r < d[0]) modify(1, 1, d[0], a[i].r + 1, d[0], i) ;
			if (a[i].l > 1) modify(1, 1, d[0], 1, a[i].l - 1, i) ;
		} else {
			if (a[i].r < a[i].l - 1) modify(1, 1, d[0], a[i].r + 1, a[i].l - 1, i) ;
		}
	}
	ll ans = 1e17 ;
	rep(i, 0, n - 1) {
		int u = query(1, 1, d[0], a[i].l) ;
		if (u == inf) ans = min(ans, 0LL) ; else ans = min(ans, fl[u] + (d[a[u].l] - d[a[i].l] + mo) % mo) ;
		u = query(1, 1, d[0], a[i].r) ;
		if (u == inf) ans = min(ans, 0LL) ; else ans = min(ans, fl[u] + (d[a[u].l] - d[a[i].r] + mo) % mo) ;
	}
	printf("%lld\n", ans + sum * 2) ; 
	return 0 ; 
}