‘vector’ was not declared in this scope, why im i getting this

‘vector’ was not declared in this scope

Ive already tried "Vector vector" and "using vector"

#include <iostream>

using namespace std;

int main(){
    vector <int>input(5);
    for(int x = 0; x < 5; x++){
    input.push_back(x);
    }
    for(int x = 0; x < 5; x++){
    cout<<input[x];
    }
}