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#include <iostream>
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using namespace std;
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int main()
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{
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    int n, p, q, f=0;
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    cin >> n;
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    for (int i = 1; i <= n; i++) {
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        cin >> p >> q;
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        if (q - p >=2) {
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            f++;
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        }
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    }
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    cout << f;
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}