vector<vector<int>>dp(s1.size() + 1, vector<int>(s2.size() + 1, 0));

for(int i = 0; i <= s1.size(); i++) {

dp[i][0] = i;

}

for(int j = 0; j <= s2.size(); j++) {

dp[0][j] = j;

}

for(int i = 1; i <= s1.size(); i++) {

for(int j = 1; j <= s2.size(); j++) {

if(s1[i - 1] == s2[j - 1]) {

dp[i][j] = dp[i - 1][j - 1];

} else {

dp[i][j] = min(dp[i - 1][j] + 1, dp[i][j - 1] + 1);

}

}

}

return dp[s1.size()][s2.size()];

}