#include <fstream>
#include <algorithm>
#define x first
#define y second
using namespace std;
class InputReader {
    public:
        InputReader() {}
        InputReader(const char *file_name) {
            input_file = fopen(file_name, "r");
            cursor = 0;
            fread(buffer, SIZE, 1, input_file);
        }
        inline InputReader &operator >>(int &n) {
            while((buffer[cursor] < '0' || buffer[cursor] > '9')&&buffer[cursor]!='-') {
                advance();
            }
            n =0;
            semn= 1;
            if(buffer[cursor]=='-') semn=-1,advance();
            while('0' <= buffer[cursor] && buffer[cursor] <= '9') {
                n = n * 10 + buffer[cursor] - '0';
                advance();
            }
            n*=semn;
            return *this;
        }
    private:
        FILE *input_file;
        static const int SIZE = 1 << 17;
        int cursor,semn;
        char buffer[SIZE];
        inline void advance() {
            ++ cursor;
            if(cursor == SIZE) {
                cursor = 0;
                fread(buffer, SIZE, 1, input_file);
            }
        }
}f("pq.in");
ofstream g("pq.out");
int n,t,i,step,xi,a,b,nr,v[1<<17],V[1<<17];
int main()
{
    f>>n>>t;
    for(i=1;i<=n;++i)
    {
        f>>xi;
        V[v[xi]]=i;
        v[xi]=i;
    }
    //sort(V+1,V+nr+1,cmp());
    while(t--)
    {
        f>>a>>b;
        int sol=-1;
        while(a<=b)
        {
            if(V[a]<=b)
            {
                sol=max(V[a]-a,sol);

            }
            ++a;
        }
        g<<sol<<'\n';
    }
    return 0;
}