#include<bits/stdc++.h>
using namespace std;

#define REP(i,a,b) for(i=a;i<b;i++)
#define rep(i,n) REP(i,0,n)

#define mygc(c) (c)=getchar_unlocked()
#define mypc(c) putchar_unlocked(c)

#define ll long long
#define ull unsigned ll

void reader(int *x){int k,m=0;*x=0;for(;;){mygc(k);if(k=='-'){m=1;break;}if('0'<=k&&k<='9'){*x=k-'0';break;}}for(;;){mygc(k);if(k<'0'||k>'9')break;*x=(*x)*10+k-'0';}if(m)(*x)=-(*x);}
void reader(ll *x){int k,m=0;*x=0;for(;;){mygc(k);if(k=='-'){m=1;break;}if('0'<=k&&k<='9'){*x=k-'0';break;}}for(;;){mygc(k);if(k<'0'||k>'9')break;*x=(*x)*10+k-'0';}if(m)(*x)=-(*x);}
void reader(double *x){scanf("%lf",x);}
int reader(char c[]){int i,s=0;for(;;){mygc(i);if(i!=' '&&i!='\n'&&i!='\r'&&i!='\t'&&i!=EOF) break;}c[s++]=i;for(;;){mygc(i);if(i==' '||i=='\n'||i=='\r'||i=='\t'||i==EOF) break;c[s++]=i;}c[s]='\0';return s;}
template <class T, class S> void reader(T *x, S *y){reader(x);reader(y);}
template <class T, class S, class U> void reader(T *x, S *y, U *z){reader(x);reader(y);reader(z);}
template <class T, class S, class U, class V> void reader(T *x, S *y, U *z, V *w){reader(x);reader(y);reader(z);reader(w);}

void writer(int x, char c){int s=0,m=0;char f[10];if(x<0)m=1,x=-x;while(x)f[s++]=x%10,x/=10;if(!s)f[s++]=0;if(m)mypc('-');while(s--)mypc(f[s]+'0');mypc(c);}
void writer(ll x, char c){int s=0,m=0;char f[20];if(x<0)m=1,x=-x;while(x)f[s++]=x%10,x/=10;if(!s)f[s++]=0;if(m)mypc('-');while(s--)mypc(f[s]+'0');mypc(c);}
void writer(double x, char c){printf("%.15f",x);mypc(c);}
void writer(const char c[]){int i;for(i=0;c[i]!='\0';i++)mypc(c[i]);}
void writer(const char x[], char c){int i;for(i=0;x[i]!='\0';i++)mypc(x[i]);mypc(c);}
template<class T> void writerLn(T x){writer(x,'\n');}
template<class T, class S> void writerLn(T x, S y){writer(x,' ');writer(y,'\n');}
template<class T, class S, class U> void writerLn(T x, S y, U z){writer(x,' ');writer(y,' ');writer(z,'\n');}
template<class T> void writerArr(T x[], int n){int i;if(!n){mypc('\n');return;}rep(i,n-1)writer(x[i],' ');writer(x[n-1],'\n');}

char memarr[17000000]; void *mem = memarr;
#define MD 1000000007

template<class S, class T> inline void chmin(S &a, T b){if(a>b)a=b;}
template<class S, class T> inline void chmax(S &a, T b){if(a<b)a=b;}

int N;
char in[111];
char dp[21][21][21][21];

int main(){
  int i, j, k;
  int a,b,c,d,e;
  int mx,res;

  N = reader(in);
  mx = N / 5;

  for(a=mx;a>=0;a--) for(b=a;b>=0;b--) for(c=b;c>=0;c--) for(d=c;d>=0;d--) dp[a][b][c][d] = -1;
  dp[0][0][0][0] = 0;
  rep(i,N){
    for(a=mx;a>=0;a--) for(b=a;b>=0;b--) for(c=b;c>=0;c--) for(d=c;d>=0;d--) if(dp[a][b][c][d]>=0){
      if(a && dp[a-1][b][c][d] <= dp[a][b][c][d]) dp[a-1][b][c][d] = -1;
      if(b&&b>c && dp[a][b-1][c][d] <= dp[a][b][c][d]) dp[a][b-1][c][d] = -1;
      if(c&&c>d && dp[a][b][c-1][d] <= dp[a][b][c][d]) dp[a][b][c-1][d] = -1;
      if(in[i]=='K' || in[i]=='?'){
        if(a<mx) chmax(dp[a+1][b][c][d], dp[a][b][c][d]);
      }
      if(in[i]=='U' || in[i]=='?'){
        if(b<a) chmax(dp[a][b+1][c][d], dp[a][b][c][d]);
      }
      if(in[i]=='R' || in[i]=='?'){
        if(c<b) chmax(dp[a][b][c+1][d], dp[a][b][c][d]);
      }
      if(in[i]=='O' || in[i]=='?'){
        if(d<c) chmax(dp[a][b][c][d+1], dp[a][b][c][d]);
      }
      if(in[i]=='I' || in[i]=='?'){
        if(dp[a][b][c][d]<d) dp[a][b][c][d]++;
      }
    }
  }

  res = 0;
  rep(a,mx+1) rep(b,a+1) rep(c,b+1) rep(d,c+1) chmax(res, dp[a][b][c][d]);
  writerLn(res);

  return 0;
}