#include <bits/stdc++.h>
using namespace std;
#define int long long
int n,ans,dp[200005][3];
string s;
signed main(){
ios::sync_with_stdio(false);
cin.tie(0),cout.tie(0);
cin>>n;
cin>>s;
s=' '+s;
for(int i=1;i<=n;i++){
for(int j=0;j<3;j++){
if(s[i]=='R' && j==2){
continue;
}else if(s[i]=='P' && j==0){
continue;
}else if(s[i]=='S' && j==1){
continue;
}else{
if(s[i]=='R' && j==1){
dp[i][j]=max(dp[i-1][0],dp[i-1][2])+1;
}else if(s[i]=='P' && j==2){
dp[i][j]=max(dp[i-1][0],dp[i-1][1])+1;
}else if(s[i]=='S' && j==0){
dp[i][j]=max(dp[i-1][1],dp[i-1][2])+1;
}else{
if(s[i]=='R'&& j==0){
dp[i][j]=max(dp[i-1][1],dp[i-1][2]);
}else if(s[i]=='P'&& j==1){
dp[i][j]=max(dp[i-1][0],dp[i-1][2]);
}else if(s[i]=='S'&& j==2){
dp[i][j]=max(dp[i-1][0],dp[i-1][1]);
}
}
}
}
}
cout<<max(dp[n][0],max(dp[n][1],dp[n][2]));
return 0;
}
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