To some string S, we will perform some replacement operations that replace groups of letters with new ones (not necessarily the same size). Each replacement operation has 3 parameters: a starting index i, a source word x and a target word y. The rule is that if x starts at position i in the original string S, then we will replace that occurrence of x with y. If not, we do nothing. For example, if we have S = "abcd" and we have some replacement operation i = 2, x = "cd", y = "ffff", then because "cd" starts at position 2 in the original string S, we will replace it with "ffff". Using another example on S = "abcd", if we have both the replacement operation i = 0, x = "ab", y = "eee", as well as another replacement operation i = 2, x = "ec", y = "ffff", this second operation does nothing because in the original string S[2] = 'c', which doesn't match x[0] = 'e'. All these operations occur simultaneously. It's guaranteed that there won't be any overlap in replacement: for example, S = "abc", indexes = [0, 1], sources = ["ab","bc"] is not a valid test case. Example 1: Input: S = "abcd", indexes = [0, 2], sources = ["a", "cd"], targets = ["eee", "ffff"] Output: "eeebffff" Explanation: "a" starts at index 0 in S, so it's replaced by "eee". "cd" starts at index 2 in S, so it's replaced by "ffff". Example 2: Input: S = "abcd", indexes = [0, 2], sources = ["ab","ec"], targets = ["eee","ffff"] Output: "eeecd" Explanation: "ab" starts at index 0 in S, so it's replaced by "eee". "ec" doesn't starts at index 2 in the original S, so we do nothing. Constraints: 0 <= S.length <= 1000 S consists of only lowercase English letters. 0 <= indexes.length <= 100 0 <= indexes[i] < S.length sources.length == indexes.length targets.length == indexes.length 1 <= sources[i].length, targets[i].length <= 50 sources[i] and targets[i] consist of only lowercase English letters.