diff --git a/codeforces/CF590D.cpp b/codeforces/CF590D.cpp
new file mode 100644
index 0000000..7604ec2
--- /dev/null
+++ b/codeforces/CF590D.cpp
@@ -0,0 +1,107 @@
+// https://codeforces.com/contest/1234
+
+#include<bits/stdc++.h>
+using namespace std;
+#define ll long long
+#define pb push_back
+#define mp make_pair
+#define pii pair<int,int>
+#define ppi pair< pair<int,int>,int >
+#define bs binary_search
+#define gcd _gcd
+#define fs first
+#define sc second
+int ABS(int a){return max(a,-a);}
+ll ABS(ll a){return max(a,-a);}
+double ABS(double a){return max(a,-a);}
+int gif(int x,int a){return (x%a==0)?(x/a):((x/a)+1);}
+ll gif(ll x,ll a){return (x%a==0LL)?(x/a):((x/a)+1LL);}
+int lif(int x,int a){return (x/a);}
+ll lif(ll x,ll a){return (x/a);}
+
+struct fenwick
+{
+    vector<ll> t;
+
+    void reset(int n)
+    {
+        t.assign(n+1, 0);
+    }
+
+    void update(int p, ll v)
+    {
+        for (; p < (int)t.size(); p += (p&(-p))) t[p] += v;
+    }
+
+    ll query(int r) //finds [1, r] sum
+    {                     
+        ll sum = 0;
+        for (; r; r -= (r&(-r))) sum += t[r];
+        return sum;
+    }
+
+    ll query(int l, int r) //finds [l, r] sum
+    {
+        if(l == 0) return query(r);
+        return query(r) - query(l-1);
+    }
+};
+
+int main()
+{
+    /*#ifndef ONLINE_JUDGE
+    freopen("input.txt","r",stdin);
+    freopen("output.txt","w",stdout);
+    #endif*/
+
+    ios::sync_with_stdio(0);
+    cin.tie(0);
+
+    string s;
+    cin>>s;
+    s="."+s; // for 1-based indexing
+    int n = s.size();
+
+     // fenwick tree for all characters
+    fenwick fen[26];
+    for(int i=0;i<26;i++)
+        fen[i].reset(n+1);
+    
+    //updates count of s[i] in the respective fenwick tree
+    for(int i=1;i<=n;i++)
+        fen[s[i]-'a'].update(i,1LL);
+        
+    int q;
+    cin>>q;
+    while(q--)
+    {
+        int x;
+        cin>>x;
+        
+        if(x==1)
+        {
+            int pos;char c;
+            cin>>pos>>c;
+            
+            // to remove its freq from the fenwick tree
+            fen[s[pos]-'a'].update(pos,-1LL);
+            s[pos]=c;
+            // to add its freq in the fenwick tree
+            fen[s[pos]-'a'].update(pos,1LL);
+        }
+        else
+        {
+            int l,r;
+            cin>>l>>r;
+            int ans=0;
+
+            // number of distinct characters count
+            for(int i=0;i<26;i++)
+                if(fen[i].query(l,r)>0)
+                    ans++;
+            cout<<ans<<"\n";
+        }
+    }
+    
+
+}