Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
X = list(input())
es = [0,N,0]

def p(X):
    print(X)

def list_change(X):
    for i in range(N):
        if X[i] == 'W':
            es[0] = i
            for j in reversed(range(es[1])):
                if X[j] == 'R':
                    es[1] = j
                    if i<j :
                        X[i] = 'R'
                        X[j] = 'W'
                        es[2] +=1
                        break
                elif j == 0:
                    break


list_change(X)
p(es[2])


Fixed submission:
N = int(input())
X = list(input())
es = [0,N,0]

def p(X):
    print(X)

def list_change(X):
    for i in range(N):
        if X[i] == 'W':
            es[0] = i
            for j in reversed(range(es[1])):
                if X[j] == 'R':
                    es[1] = j
                    if i<j :
                        X[i] = 'R'
                        X[j] = 'W'
                        es[2] +=1
                        break
                elif j == 0:
                    es[1] = 1
                


list_change(X)
p(es[2])

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
X = list(input())
es = [0,N,0]

def p(X):
    print(X)

def list_change(X):
    for i in range(N):
        if X[i] == 'W':
            es[0] = i
            for j in reversed(range(es[1])):
                if X[j] == 'R':
                    es[1] = j
                    if i<j :
                        X[i] = 'R'
                        X[j] = 'W'
                        es[2] +=1
                        break
                   


list_change(X)
p(es[2])


Fixed submission:
N = int(input())
X = list(input())
es = [0,N,0]

def p(X):
    print(X)

def list_change(X):
    for i in range(N):
        if X[i] == 'W':
            es[0] = i
            for j in reversed(range(es[1])):
                if X[j] == 'R':
                    es[1] = j
                    if i<j :
                        X[i] = 'R'
                        X[j] = 'W'
                        es[2] +=1
                        break
                elif j == 0:
                    es[1] = 1
                


list_change(X)
p(es[2])

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
X = list(input())
es = [0,N,0]

def p(X):
    print(X)

def list_change(X):
    for i in range(N):
        if X[i] == 'W':
            es[0] = i
            for j in reversed(range(N)):
                if X[j] == 'R':
                    es[1] = j
                    if i<j :
                        X[i] = 'R'
                        X[j] = 'W'
                        es[2] +=1
                        break
                   


list_change(X)
p(es[2])


Fixed submission:
N = int(input())
X = list(input())
es = [0,N,0]

def p(X):
    print(X)

def list_change(X):
    for i in range(N):
        if X[i] == 'W':
            es[0] = i
            for j in reversed(range(es[1])):
                if X[j] == 'R':
                    es[1] = j
                    if i<j :
                        X[i] = 'R'
                        X[j] = 'W'
                        es[2] +=1
                        break
                elif j == 0:
                    es[1] = 1
                


list_change(X)
p(es[2])