PROG-T1088: Iguana

#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

int main(){

    int ni, nc;
    scanf("%d", &ni);
    scanf("%d", &nc);
    vector<int> L, R;
    vector<int> events = {1, ni + 1};
    for(int i = 1; i <= nc; ++i){
        int l, r;
        scanf("%d", &l);
        scanf("%d", &r);
        L.push_back(l);
        R.push_back(r);
        events.push_back(l);
        events.push_back(r + 1);
    }
    sort(events.begin(), events.end());
    events.resize(unique(events.begin(), events.end()) - events.begin());

    vector<int> lizard(events.size(), 0); /// 0 = R 1 = G 2 = B
    for(int i = 0; i < nc; ++i){
        int indexl = lower_bound(events.begin(), events.end(), L[i]) - events.begin();
        int indexr = lower_bound(events.begin(), events.end(), R[i] + 1) - events.begin();
        ++lizard[indexl];
        --lizard[indexr];
    }

    char tmp;
    int tr;
    scanf(" %c", &tmp);
    switch(tmp){
    case 'R':
        tr = 0;
        break;
    case 'G':
        tr = 1;
        break;
    case 'B':
        tr = 2;
        break;
    }

    int sum = 0;
    lizard[0] %= 3;
    for(int i = 1; i < events.size(); ++i){
        lizard[i] += lizard[i - 1];
        lizard[i] %= 3;
        if(lizard[i] < 0){
            lizard[i] += 3;
        }
        if(lizard[i - 1] < tr){
            sum += (events[i] - events[i - 1]) * (tr - lizard[i - 1]);
        } else if(lizard[i - 1] > tr){
            sum += (events[i] - events[i - 1]) * (3 + tr - lizard[i - 1]);
        }
    }

    cout << sum;

    return 0;
}