#include<map>
#include<stdio.h>
#include<iostream>
#include<vector>
#include<algorithm>
#include<string>
#include<string.h>

#ifdef LOCAL
#define eprintf(...) fprintf(stderr, __VA_ARGS__)
#else
#define NDEBUG
#define eprintf(...) do {} while (0)
#endif
#include<cassert>

using namespace std;

typedef long long LL;
typedef vector<int> VI;

#define REP(i,n) for(int i=0, i##_len=(n); i<i##_len; ++i)
#define EACH(i,c) for(__typeof((c).begin()) i=(c).begin(),i##_end=(c).end();i!=i##_end;++i)

template<class T> inline void amin(T &x, const T &y) { if (y<x) x=y; }
template<class T> inline void amax(T &x, const T &y) { if (x<y) x=y; }
template<class Iter> void rprintf(const char *fmt, Iter begin, Iter end) {
    for (bool sp=0; begin!=end; ++begin) { if (sp) putchar(' '); else sp = true; printf(fmt, *begin); }
    putchar('\n');
}

struct Data {
    LL pos, pos2;
    LL left, right;
    LL cst;

    Data(){}

    Data(LL pos_, LL pos2_, LL left_, LL right_, LL cst_) {
	pos = pos_;
	pos2 = pos2_;
	left = left_;
	right = right_;
	cst = cst_;
    }
};

int N;
LL K;
LL A[100011];
int B[100011];
LL X[100011];
LL Y[100011];

void MAIN() {
    scanf("%d%lld", &N, &K);
    LL H = K;
    K *= 2;
    REP (i, N) scanf("%lld%d", A+i, B+i), A[i] *= 2;

    REP (i, N) if (B[i] == 1 && A[i]*2 > K) {
	puts("-1");
	return;
    }

    LL sum = 0;
    REP (i, N) sum += A[i];

    REP (t, 2) {
	LL apos = 0;
	map<LL, Data> mp;
	vector<Data> vs;

	REP (i_, N) {
	    int i = t? N-1-i_: i_;
	    // (apos, anxt];
	    LL anxt = apos + A[i];
	    LL cst = anxt*2;

	    auto it = mp.lower_bound(anxt % H);
	    if (it == mp.end()) {
		cst = 2 * anxt;
	    } else {
		Data d = it->second;
		LL ri = d.right % H;
		LL le = ri - (d.right - d.left);
		if (ri < anxt % H) {
		    ri += H;
		    le += H;
		}

		if (le < anxt % H) {
		    assert(anxt > d.right);
		    LL diff = anxt - d.right;
		    LL r = (-2*diff % K + K) % K;
		    cst = d.cst + 2 * diff + r;
		} else {
///		    eprintf("%lld x %lld\n", ri - le, d.right - d.left);
		    cst = 2 * anxt;
		}
	    }

	    (t? Y[i]: X[i+1]) = cst;

	    if (B[i] == 1) {
		if (A[i] >= H) {
		    mp.clear();
		    mp[anxt%H] = Data(anxt%H-A[i], anxt%H, apos, anxt, cst);
		    mp[anxt%H+H] = Data(anxt%H+H-A[i], anxt%H+H, apos, anxt, cst);
		} else {
		    LL right = anxt % H - H, left = right - A[i];
		    while (right <= K * 2) {
			auto z = mp.upper_bound(left);
			while (z != mp.end()) {
			    Data g = z->second;
			    if (right <= g.pos || g.pos2 <= left) {
				break;
			    }

			    if (g.pos < left) {
				mp[left] = Data(g.pos, left, g.left, g.right, g.cst);
			    }
			    mp.erase(z++);
			    if (right < g.pos2) {
				z = mp.emplace(g.pos2, Data(right, g.pos2, g.left, g.right, g.cst)).first;
			    }
			}
			left += H;
			right += H;
		    }

		    mp[anxt%H] = Data(anxt%H-A[i], anxt%H, apos, anxt, cst);
		    mp[anxt%H+H] = Data(anxt%H+H-A[i], anxt%H+H, apos, anxt, cst);
		}

	    }

	    apos += A[i];
	}
    }

    LL ans = 1LL<<60;
    if (sum <= H) ans = sum * 2;
    REP (i, N+1) amin(ans, X[i] + Y[i]);

    assert(ans % 2 == 0);
    printf("%lld\n", ans / 2);
}

int main() {
    int TC = 1;
//    scanf("%d", &TC);
    REP (tc, TC) MAIN();
    return 0;
}



Measured memory_bytes: 21504