# include <cstdio>
# include <cstring>

const char *FIN = "perb.in", *FOU = "perb.out", *adn = { "ACGT" } ;
const size_t MAX = 605 ;

char S[MAX] ;
size_t A[MAX][MAX], B[MAX][MAX] ;
size_t N, M ;

inline size_t max ( size_t a, size_t b ) {
    return (a > b ? a : b) ;
}

inline size_t min ( size_t a, size_t b ) {
    return (a < b ? a : b) ;
}

inline void solve ( size_t K ) {
    size_t aux, auxdf ;
    for ( size_t i = N; i ; --i ) {
        for ( size_t j = 0, see = i + K > N; j < 4; ++j ) {
            B[i][j] = (S[i] == adn[j]) + (see ? 0 : B[i + K][j]) ;
        }
    }

    for ( size_t i = 1; i <= N; ++i ) {
        for ( size_t j = i + 2 * K - 1; j <= N; j += K ) {
            aux = 0;
            for ( size_t k = 0; k < K; ++k ) {
                auxdf = 0 ;
                for ( size_t l = 0, see = j + k + 1 <= N; l < 4; ++l ) {
                    auxdf = max (auxdf, B[i + k][l] - (see ? B[j + k + 1][l] : 0)) ;
                }
                aux += (j - i + 1) / K - auxdf ;
            }
            A[i][j] = min (A[i][j], aux) ;
        }
    }
}

int main (void) {
    freopen (FIN, "r", stdin) ;
    freopen (FOU, "w", stdout) ;

    scanf ( "%u %u\n", &N, &M ) ;
    fgets ( S + 1, MAX, stdin ) ;

    for ( size_t i = 1; i <= N; ++i ) {
        for ( size_t j = i + 1; j <= N; ++j ) {
            A[i][j] = j - i ;
        }
    }

    for ( size_t i = 1, j = N >> 1; i <= j; ++i ) {
        solve (i) ;
    }

    for ( size_t i = 1, x, y; i <= M; ++i ) {
        scanf ( "%d %d", &x, &y ) ;
        printf ( "%d\n", A[x][y] ) ;
    }
}