N22

#include<iostream>
#include<string>

using namespace std;

int main()
{
    int n, m, l, r;
    cin >> n >>m;
    string a;
    cin >> a;
    for (int i = 0; i < m; i++)
    {
        cin >> l >> r;
        for (int j = l - 1; j < r; j++)
        {
            if (a[j] == '1') a[j] = '0';
            else if (a[j] == '0') a[j] = '1';
        }
    }
    int counter = 0;
    int tempcounter = 0;
    for (int i = 0; i < n; i++)
    {
        if (a[i] != a[i+1]) tempcounter++;
        else if (a[i] == a[i+1] && counter < tempcounter)
        {
            counter = tempcounter + 1;
            tempcounter = 0;
        }
    }
    cout << counter;
}