Iguana

/*
    Task    : Iguana
    Author  : Phumipat C. [MAGCARI]
    Language: C++
    Created : 13 October 2022 [21:20]
*/
#include<bits/stdc++.h>
using namespace std;
vector<pair<int ,int > > v;
int main(){
    int n,m,want,now = 0,ans = 0;
    scanf("%d %d",&n,&m);
    for(int i=1;i<=m;i++){
        int a,b;
        scanf("%d %d",&a,&b);
        v.push_back({a,1});
        v.push_back({b+1,-1});
    }
    v.push_back({1,0});
    v.push_back({n+1,0});
    sort(v.begin(),v.end());
    char c;
    scanf(" %c",&c);
    if(c == 'R')        want = 0;
    else if(c == 'G')   want = 1;
    else if(c == 'B')   want = 2;
    for(int i=0;i<v.size()-1;i++){
        now+=v[i].second;
        ans+=((want-(now%3)+3)%3)*(v[i+1].first-v[i].first);
    }
    printf("%d\n",ans);
    return 0;
}