**QUESTION**

Given two strings,a and b, find and print the total number of ways to insert a character at any position in string a such that the length of the Longest Common Subsequence of characters in the two strings increases by one.\n\nInput Format\n\nThe first line contains a single string denoting a. \nThe second line contains a single string denoting b.\n\nConstraints\n\nScoring\n1.1<=|a|,|b|<=5000\n2.Strings a and b are alphanumeric (i.e., consisting of arabic digits and/or upper and lower case English letters).\n3.The new character being inserted must also be alphanumeric (i.e., a digit or upper/lower case English letter).\nSubtask\n1<=|a|,|b|<=1000\n for 66.7% of the maximum score.\nOutput Format\n\nPrint a single integer denoting the total number of ways to insert a character into string a in such a way that the length of the longest common subsequence of a and b increases by one.

**ANSWER**

```
#include <bits/stdc++.h>
using namespace std;
int N, M;
char S[5002];
char T[5002];
int dp[5002][5002];
int dp2[5002][5002];
bool ok[256];
int main()
{
scanf("%s", S+1);
N=strlen(S+1);
scanf("%s", T+1);
M=strlen(T+1);
for(int i=1; i<=N; i++) for(int j=1; j<=M; j++)
{
if(S[i]==T[j])
dp[i][j]=dp[i-1][j-1]+1;
else
dp[i][j]=max(dp[i-1][j], dp[i][j-1]);
}
for(int i=N; i>=1; i--) for(int j=M; j>=1; j--)
{
if(S[i]==T[j])
dp2[i][j]=dp2[i+1][j+1]+1;
else
dp2[i][j]=max(dp2[i+1][j], dp2[i][j+1]);
}
int lcs=dp[N][M];
int ans=0;
for(int i=0; i<=N; i++)
{
for(int j=1; j<=M; j++)
{
if(dp[i][j-1]+dp2[i+1][j+1]==lcs)
ok[(int)T[j]]=true;
}
for(int j=0; j<256; j++)
{
ans+=ok[j];
ok[j]=false;
}
}
printf("%d\n", ans);
return 0;
}
```