#include<cstdio>
#include<cstring>
using namespace std;
int i,j,pas,INF,n,Q,egal[2][603][603],dp[603][603],a[603][603];
char sir[603];
int main()
{
freopen("perb.in","r",stdin);
freopen("perb.out","w",stdout);
INF=(1<<30);
scanf("%d",&n);
scanf("%d\n",&Q);
gets(sir+1);
for(i=1;i<=n;i++)
    for(j=i;j<=n;j++)
        dp[i][j]=INF;
for(pas=1;pas*2<=n;pas++)
{
    for(i=1;i+pas-1<=n;i++)
        for(j=i+1;j+pas-1<=n;j++)
            egal[pas&1][i][j]=egal[(pas&1)^1][i][j]+(sir[i+pas-1]!=sir[j+pas-1]);
    for(i=1;i+pas-1<=n;i++)
    {
        j=i+pas-1;
        a[i][j]=0;
        for(j=i+2*pas-1;j<=n;j+=pas)
        {
            a[i][j]=a[i][j-pas]+egal[pas&1][i][j-pas+1];
            if(a[i][j]<dp[i][j])
            {
                if(i==1&&j==3)
                    sir[0]=0;
                dp[i][j]=a[i][j];
            }
        }
    }
}
while(Q)
{
    Q--;
    scanf("%d %d",&i,&j);
    printf("%d\n",dp[i][j]);
}
return 0;
}