```cpp
#include<iostream>
#include<string>
#include<cstring>
using namespace std;
int main()
{
char a[1001][1001];
int n,m;
cin>>n>>m;
for(int i=1;i<=n;i++)
{
for(int j=1;j<=m;j++)
cin>>a[i][j];
}
int w=0,b=0,r=0;
int minn=10010;
for(int i=1;i<n-1;i++)
{
for(int i1=1;i1<=m;i1++)
{
if(a[i][i1]!='W') w++;
}
for(int i2=i+1;i2<n;i2++)
{
for(int j=1;j<=m;j++){
if(a[i2][j]!='B') b++;
}
for(int i3=i2+1;i3<=n;i3++)
{
for(int k=1;k<=m;k++)
{
if(a[i3][k]!='R') r++;
}
}
}
minn=min(minn,w+r+b);
w=0;
r=0;
b=0;
}
cout<<minn;
return 0;
}
by SPFA @ 2020-11-03 17:20:22